Qreator won't start when called with LC_ALL=C

While doing some testing to load Qreator in English, I noted the following:

$ LC_ALL=C qreator

Traceback (most recent call last):
  File "/usr/bin/qreator", line 47, in <module>
    qreator.main()
  File "/usr/lib/python2.7/dist-packages/qreator/__init__.py", line 63, in main
    window = QreatorWindow.QreatorWindow()
  File "/usr/lib/python2.7/dist-packages/qreator_lib/Window.py", line 48, in __new__
    new_object.finish_initializing(builder)
  File "/usr/lib/python2.7/dist-packages/qreator/QreatorWindow.py", line 73, in finish_initializing
    self.init_about_dialog()
  File "/usr/lib/python2.7/dist-packages/qreator/QreatorWindow.py", line 206, in init_about_dialog
    if default_locale.split('_')[0] != 'ca':
AttributeError: 'NoneType' object has no attribute 'split'

So it seems I introduced a regression while fixing bug 1031657