Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/openshot/windows/MainGTK.py", line 1781, in on_tlbImportFiles_clicked
    self.import_files_dialog = AddFiles.frmAddFiles(form=self, project=self.project)
  File "/usr/lib/python2.6/site-packages/openshot/windows/AddFiles.py", line 47, in __init__
    self.frmAddFiles.set_current_folder(preferences.Settings.app_state["import_folder"])
TypeError: Gtk.FileChooser.set_current_folder() argument 1 must be string, not None
on_tlbImportFiles_clicked called with self.GtkToolButton