Can not take screenshot: "No valid filetype specified"

Hi,

I just doing `dist-upgrade` and after that the shutter is not working with message "No valid filetype specified"

Extra info:

```
$ shutter
WARNING: Image::ExifTool is missing --> writing Exif information will be disabled!

WARNING: Gtk2::AppIndicator is missing --> there will be no icon showing up in the status bar when running Unity!

Use of uninitialized value in pattern match (m//) at /usr/bin/shutter line 6152.
Use of uninitialized value in pattern match (m//) at /usr/bin/shutter line 6152.
Use of uninitialized value in pattern match (m//) at /usr/bin/shutter line 6152.
```

I'm using Shutter 0.93.1 on Linux Mint 18.2 64-bit