cannot open project

I use version 1.4.3 on ubuntu 16.04.
Suddenly i can't open an .osp file. I get this error "There was an error opening this project file. Please be sure you open the correct *.osp file".I can open another projects.

Console messages:
/usr/share/openshot/openshot/classes/sequences.py:781: GtkWarning: gdk_pixbuf_scale_simple: assertion 'dest_width > 0' failed
  new_pixbuf = pixbuf.scale_simple(remaining_pixels, height, gtk.gdk.INTERP_NEAREST)
Traceback (most recent call last):
  File "/usr/share/openshot/openshot/windows/MainGTK.py", line 2508, in on_hsZoom_value_changed
    self.project.Render()
  File "/usr/share/openshot/openshot/classes/project.py", line 221, in Render
    self.sequences[0].Render()
  File "/usr/share/openshot/openshot/classes/sequences.py", line 171, in Render
    MyTrack.Render()
  File "/usr/share/openshot/openshot/classes/track.py", line 94, in Render
    MyClip.Render()
  File "/usr/share/openshot/openshot/classes/clip.py", line 287, in Render
    self.RenderClip()
  File "/usr/share/openshot/openshot/classes/clip.py", line 1163, in RenderClip
    pixbuf_width = pixbuf.get_width()
AttributeError: 'NoneType' object has no attribute 'get_width'
on_mnuOpenProject_activate called with self.GtkImageMenuItem

Thank you

Kind regards