Cannot access right-click menu in first library folder

To clarify: the first folder is affected by this and the second folder is fine.

Could you do the same thing using an instance of DAP launched from a terminal? I guess there will be an error message displayed there.

I have attached the output from running DAP from the terminal. All I did was load it up and right click in the first library folder.

(and here's the exception raised)

Traceback (most recent call last):
  File "/usr/share/decibel-audio-player/src/modules/Library.py", line 804, in onButtonPressed
    self.showPopupMenu(tree, event.button, event.time, path)
  File "/usr/share/decibel-audio-player/src/modules/Library.py", line 553, in showPopupMenu
    genreItem = gtk.CheckMenuItem(genre.capitalize())
TypeError: GtkCheckMenuItem.__init__() argument 1 must be string without null bytes or None, not str

It looks like some of your tracks have a genre that cannot be handled (like an invalid string of characters). There's a file named 'genres' in '~/.config/decibel-audio-player/Library/XXX/' where XXX is the name of the library that causes this problem. Could you attach it to this report?

Certainly. Please find it attached (it's rather long).