Here's my complete debug output for this bug on my machine, as requested:

Nuvola     Info main.vala:118: Welcome to Nuvola Player, version: 2.0.4
    Nuvola     Info main.vala:122: Revision: 627, <email address hidden>
    Nuvola     Info main.vala:123: Report any issues/bugs you might find to http://nuvolaplayer.fenryxo.cz/support/bug_reporting.html
    Nuvola    Debug main.vala:124: command: /usr/lib/nuvolaplayer/nuvolaplayer --debug
    Nuvola    Debug main.vala:126: Enabled features: Dynamic Proxy Resolver, Disk cache for remote data, Unity Quicklist, Dock Manager support, MPRIS support, console client, support for media keys, optimization of SVG images, Last.fm scrobbling, Notifications, Lyrics fetching, debug symbols
    Nuvola    Debug main.vala:127: Disabled features: experimental features
       Gtk    Debug Connecting to session manager
    Nuvola    Debug main.vala:189: Application activated
 <unknown>    Debug NP_Initialize
 <unknown>    Debug NP_Initialize succeeded
No bp log location saved, using default.
[000:000] Browser XEmbed support present: 1
[000:000] Browser toolkit is Gtk2.
[000:000] Using Gtk2 toolkit
No bp log location saved, using default.
Gtk-Message: Failed to load module "overlay-scrollbar"

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",

(npviewer.bin:3512): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
Gtk-Message: Failed to load module "canberra-gtk-module"
[003:051] No bp log location saved, using default.
[003:052] Browser XEmbed support present: 1
[003:052] Browser toolkit is Gtk2.
[003:052] Using Gtk2 toolkit
[000:000] No bp log location saved, using default.
 <unknown>    Debug NP_Initialize
 <unknown>    Debug NP_Initialize succeeded
 <unknown>    Debug NP_Initialize
 <unknown>    Debug NP_Initialize succeeded
 <unknown>    Debug NP_Initialize
 <unknown>    Debug NP_Initialize succeeded
    Nuvola    Debug main.vala:285: WebPlugin: Google Talk Plugin Video Renderer, /usr/lib/mozilla/plugins/libnpo1d.so
    Nuvola    Debug main.vala:285: WebPlugin: iTunes Application Detector, /usr/lib/mozilla/plugins/librhythmbox-itms-detection-plugin.so
    Nuvola    Debug main.vala:285: WebPlugin: Google Talk Plugin Video Renderer, /usr/lib/firefox/plugins/libnpo1d.so
    Nuvola    Debug main.vala:285: WebPlugin: Google Talk Plugin, /usr/lib/firefox/plugins/libnpgoogletalk.so
    Nuvola    Debug main.vala:285: WebPlugin: Windows Media Player Plug-in 10 (compatible; Videos), /usr/lib/mozilla/plugins/libtotem-gmp-plugin.so
    Nuvola    Debug main.vala:281: Compatible Flash: Shockwave Flash, /opt/nuvolaplayer/flash/wrapped/npwrapper.libflashplayer.so
   Diorite    Debug Max data cache size: 100
   libsoup  Warning No feature manager for feature of type 'SoupProxyURIResolver'
   Diorite    Debug Setting proxy (auto): dynamic resolver
    Nuvola    Debug extension.vala:34: new Extension: lastfm
    Nuvola     Info extensionsmanager.vala:91: Extension with id 'lastfm' loaded.
    Nuvola    Debug extension.vala:34: new Extension: mediakeys
    Nuvola     Info extensionsmanager.vala:91: Extension with id 'mediakeys' loaded.
    Nuvola    Debug extension.vala:34: new Extension: notifications
    Nuvola     Info extensionsmanager.vala:91: Extension with id 'notifications' loaded.
    Nuvola    Debug extension.vala:34: new Extension: trayicon
    Nuvola     Info extensionsmanager.vala:91: Extension with id 'trayicon' loaded.
    Nuvola    Debug extension.vala:34: new Extension: unityquicklist
    Nuvola    Debug unity_quick_list.vala:64: Unity Launcher Entry for nuvolaplayer.desktop
    Nuvola     Info extensionsmanager.vala:91: Extension with id 'unityquicklist' loaded.
    Nuvola    Debug servicesmanager.vala:94: Found service Google Play Music at /home/david/.local/share/nuvolaplayer/services/googleplay, version 3.21
    Nuvola    Debug servicesmanager.vala:105: Found service Google Play Music at /usr/share/nuvolaplayer/services/googleplay, version 3.20
    Nuvola     Info servicesmanager.vala:118: Using service Google Play Music from /home/david/.local/share/nuvolaplayer/services/googleplay, version 3.21
    Nuvola    Debug service.vala:297: ~Service
    Nuvola    Debug main.vala:481: Starting web interface for googleplay: https://play.google.com/music/listen#/al/David+Bowie/Best+Of+Bowie
    Nuvola    Debug jsapi.vala:438: Reset main object
   Diorite    Debug Action activated: service
   Diorite    Debug Action activated: control
   Diorite    Debug Action activated: view
   Diorite    Debug Action activated: help
   Diorite    Debug XFCE session vanished: org.xfce.SessionManager
   Diorite    Debug GNOME session appeared: org.gnome.SessionManager, :1.0
    Nuvola    Debug media_keys.vala:200: GNOME settings daemon appeared: org.gnome.SettingsDaemon, :1.5
    Nuvola    Debug jsapi.vala:495: Window object cleared
    Nuvola    Debug jsapi.vala:567: JSAPI injected successfully
    Nuvola    Debug player.vala:139: Playback state changed: none → paused
    Nuvola    Debug main.vala:853: Autoplay: false
    Nuvola    Debug player.vala:139: Playback state changed: paused → none
    Nuvola    Debug player.vala:139: Playback state changed: none → paused
    Nuvola    Debug player.vala:139: Playback state changed: paused → playing
    Nuvola    Debug player.vala:172: Album art changed: null → https://lh4.googleusercontent.com/eVwbrOi19wtBd0fuCFlvHIsPG6EydwhAAVt-77XruMqbJnFOA7OiF_uTzj0LBBEZT0AphVYxANM=s130-c-e100
    Nuvola    Debug player.vala:212: Artist changed: null → David Bowie
    Nuvola    Debug player.vala:219: Song changed: null → Space Oddity (1999 Digital Remaster)
    Nuvola    Debug player.vala:226: Album changed: null → Best Of Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug mainwindow.vala:165: ~~ Delete event
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 977 from disconnected 0x7ffe6e717e60
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1006 from disconnected 0x7ffe6e7e7500
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1028 from disconnected 0x7ffe6e7e75b0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1050 from disconnected 0x7ffe6e7e7660
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1072 from disconnected 0x7ffe6e7e7710
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1098 from disconnected 0x7ffe6e7fa020
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1124 from disconnected 0x7ffe6e7fa5a0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1160 from disconnected 0x7ffe6e717f10
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1205 from disconnected 0x7ffe6e7fa0d0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1234 from disconnected 0x7ffe6e717990
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1256 from disconnected 0x7ffe6e717ba0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1278 from disconnected 0x7ffe6e717c50
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1323 from disconnected 0x7ffe6e7fa180
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1367 from disconnected 0x7ffe6e971020
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1389 from disconnected 0x7ffe6e9710d0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1411 from disconnected 0x7ffe6e971180
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1438 from disconnected 0x7ffe6e946940
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1461 from disconnected 0x7ffe6e946a20
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1484 from disconnected 0x7ffe6e946b00
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1544 from disconnected 0x7ffe6e7e7030
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1573 from disconnected 0x7ffe6e7e7240
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1595 from disconnected 0x7ffe6e7e70e0
LIBDBUSMEN    Debug ../../../libdbusmenu-gtk/parser.c:197 tried to disconnect signal handler 1617 from disconnected 0x7ffe6e7e7190
    Nuvola    Debug mainwindow.vala:167: ~~ Queue wanna_quit_cb
    Nuvola    Debug mainwindow.vala:173: ~~ wanna_quit_cb
    Nuvola    Debug main.vala:712: On close: hide
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
    Nuvola    Debug lastfm.vala:525: Last FM update now playing: Space Oddity (1999 Digital Remaster) by David Bowie
^C   Diorite    Debug Caught signal 2, exiting ...
    Nuvola    Debug main.vala:645: Early shutdown
    Nuvola Critical player.vala:270: Player: Frame command pause failed: Google Music: 'null' is not an object
    Nuvola     Info extensionsmanager.vala:117: Extension with id 'trayicon' unloaded.
    Nuvola    Debug lastfm.vala:485: Last FM scrobble: Space Oddity (1999 Digital Remaster) by David Bowie, 1373827554
    Nuvola     Info extensionsmanager.vala:117: Extension with id 'lastfm' unloaded.
    Nuvola     Info extensionsmanager.vala:117: Extension with id 'notifications' unloaded.
    Nuvola    Debug extension.vala:87: ~Extension: notifications
    Nuvola     Info extensionsmanager.vala:117: Extension with id 'mediakeys' unloaded.
    Nuvola     Info extensionsmanager.vala:117: Extension with id 'unityquicklist' unloaded.
    Nuvola    Debug main.vala:668: Late shutdown
    Nuvola    Debug main.vala:673: User interface state saved.
    Nuvola    Debug main.vala:680: Unparent main_view
    Nuvola    Debug main.vala:685: Destroy main_view
    Nuvola    Debug main.vala:687: Destroy main_window
    Nuvola    Debug main.vala:689: User interface destroyed.
   Diorite    Debug Cache.dump()
   Diorite    Debug Cache.dump() done