Category Rules Dialog Error Output when rule with empty search string is selected

[simpsus]

Traceback (most recent call last):
  File "/home/bastian/workspace/avernus/avernus/gui/account/categorization_dialog.py", line 96, in on_cursor_changed
    self.save_active_rule()
  File "/home/bastian/workspace/avernus/avernus/gui/account/categorization_dialog.py", line 79, in save_active_rule
    self.active_rule.category = model[active_iter][0]
  File "/usr/lib/python2.7/dist-packages/gi/overrides/Gtk.py", line 782, in __getitem__
    aiter = self._getiter(key)
  File "/usr/lib/python2.7/dist-packages/gi/overrides/Gtk.py", line 776, in _getiter
    aiter = self.get_iter(key)
  File "/usr/lib/python2.7/dist-packages/gi/overrides/Gtk.py", line 798, in get_iter
    path = TreePath(path)
  File "/usr/lib/python2.7/dist-packages/gi/overrides/Gtk.py", line 1209, in __new__
    if len(path) == 0:
TypeError: object of type 'NoneType' has no len()

This happens when the first rule is created or simply upon a click on an unsaved rule without a searchstring