Activating "Patterson View" results in no images (black scene)

[mhantke]

Triggered error message:

Traceback (most recent call last):
File "/Users/hantke/Work/programs/owl/views/view2d.py", line 836, in paintGL
self._updateTextures(visible)
File "/Users/hantke/Work/programs/owl/views/view2d.py", line 1035, in _updateTextures
pattersonParams = self.data.pattersonItem.getParams(img)
AttributeError: 'NoneType' object has no attribute 'getParams'