[v1.8.8] TypeError - OpenNumismat\ListView.py:112

OpenNumismat: 1.8.8
OS: Windows 10 (10.0.19041)
Python: 3.8.3 (64bit)
Qt: 5.15.0
Locale: it

Traceback (most recent call last):
File "OpenNumismat\PageView.py", line 654, in modelChanged
File "OpenNumismat\ListView.py", line 754, in modelChanged
File "OpenNumismat\ListView.py", line 112, in modelChanged
TypeError: %d format: a number is required, not NoneType