Picard crashes when running "Restore all defaults" in options.

E:\win32\musicbrainz\picard\git>tagger.py
I: 07:32:12,792 E:\win32\musicbrainz\picard\git\picard\tagger.debug:260: Debug mode off
Traceback (most recent call last):
  File "E:\win32\musicbrainz\picard\git\picard\ui\options\dialog.py", line 182, in confirm_reset_all
    self._show_dialog(msg, self.restore_all_defaults)
  File "E:\win32\musicbrainz\picard\git\picard\ui\options\dialog.py", line 192, in _show_dialog
    function()
  File "E:\win32\musicbrainz\picard\git\picard\ui\options\dialog.py", line 171, in restore_all_defaults
    page.restore_defaults()
  File "E:\win32\musicbrainz\picard\git\picard\ui\options\cover.py", line 81, in restore_defaults
    self.provider_list_widget.clear()
AttributeError: 'CoverOptionsPage' object has no attribute 'provider_list_widget'