AttributeError in HttpUpload plugin

Here is what happens when you choose an image to send:

Traceback (most recent call last):
  File "/usr/share/gajim/src/dialogs.py", line 1488, in on_dialog_response
    self.response_ok[0](dialog, *self.response_ok[1:])
  File "/usr/share/gajim/src/dialogs.py", line 4769, in on_ok
    callback(widget, path_to_file)
  File "/home/mrdoctorwho/.local/share/gajim/plugins/httpupload/httpupload.py", line 336, in on_file_dialog_ok
    progress_window = ProgressWindow(_('Requesting HTTP Upload Slot...'), progress_messages, self.plugin, event)
  File "/home/mrdoctorwho/.local/share/gajim/plugins/httpupload/httpupload.py", line 627, in __init__
    self.dialog.set_transient_for(plugin.chat_control.parent_win.window)
AttributeError: 'NoneType' object has no attribute 'window'