[v1.6.4] AttributeError - d:\OpenNumismat\open-numismat\OpenNumismat\Reference\Reference.py:39

OpenNumismat: 1.6.4
OS: Windows 10 (10.0.16299)
Python: 3.4.4 (32bit)
Qt: 5.5.1
Locale: ru

Traceback (most recent call last):
File "d:\OpenNumismat\open-numismat\OpenNumismat\Reference\Reference.py", line 39, in data
AttributeError: 'int' object has no attribute 'isNull'