Error on entering invalid character in verse-order

Ubuntu 13.04
OpenLP trunk rev 2369 (does not occur on version 2.04)

An error occurs if in verse-order a non-existing tag/abbreviation is entered.

1) create a new song
2) edit the verse-order
3) enter a random char which is not an abbreviation for a verse-type in the current language (like 'q' or 'x' in english)
4) error-popup with traceback occurs

Entering a tag/abbreviation for a valid versetype which is not currently existing in the song does not lead to this error (is checked and notified on saving).

Traceback (most recent call last):
  File "~/openlp/trunk/openlp/plugins/songs/forms/editsongform.py", line 723, in on_verse_order_text_changed
    verses_in_order = self._extract_verse_order(self.verse_order_edit.text())
  File "~/openlp/trunk/openlp/plugins/songs/forms/editsongform.py", line 144, in _extract_verse_order
    verse_index = VerseType.from_translated_tag(item, None)
  File "~/openlp/trunk/openlp/plugins/songs/lib/__init__.py", line 234, in from_translated_tag
    if len(VerseType.names) > default:
TypeError: unorderable types: int() > NoneType()