[v1.8.3] KeyError - d:\OpenNumismat\open-numismat\OpenNumismat\ListView.py:536

OpenNumismat: 1.8.3
OS: Windows 10 (10.0.18362)
Python: 3.4.4 (32bit)
Qt: 5.5.1
Locale: cs

Traceback (most recent call last):
File "d:\OpenNumismat\open-numismat\OpenNumismat\ListView.py", line 536, in lessThan
KeyError: 'Owned'