[v1.8.6] AttributeError - c:\python\32-bit\3.4\lib\warnings.py:15

OpenNumismat: 1.8.6
OS: Windows 10 (10.0.19640)
Python: 3.4.4 (32bit)
Qt: 5.5.1
Locale: en

Traceback (most recent call last):
File "OpenNumismat\PageView.py", line 644, in modelChanged
File "OpenNumismat\StatisticsView.py", line 677, in modelChanged
File "OpenNumismat\StatisticsView.py", line 220, in setData
File "C:\Python34\lib\site-packages\matplotlib\backends\backend_qt5agg.py", line 127, in draw
File "C:\Python34\lib\site-packages\matplotlib\backends\backend_agg.py", line 430, in draw
File "C:\Python34\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
File "C:\Python34\lib\site-packages\matplotlib\figure.py", line 1295, in draw
File "C:\Python34\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
File "C:\Python34\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
File "C:\Python34\lib\site-packages\matplotlib\axes\_base.py", line 2399, in draw
File "C:\Python34\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
File "C:\Python34\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
File "C:\Python34\lib\site-packages\matplotlib\axis.py", line 1135, in draw
File "C:\Python34\lib\site-packages\matplotlib\axis.py", line 1075, in _get_tick_bboxes
File "C:\Python34\lib\site-packages\matplotlib\text.py", line 970, in get_window_extent
File "C:\Python34\lib\site-packages\matplotlib\text.py", line 363, in _get_layout
File "C:\Python34\lib\site-packages\matplotlib\backends\backend_agg.py", line 231, in get_text_width_height_descent
File "C:\Python34\lib\site-packages\matplotlib\mathtext.py", line 3290, in parse
File "C:\Python34\lib\site-packages\matplotlib\mathtext.py", line 881, in __init__
File "C:\Python34\lib\site-packages\matplotlib\mathtext.py", line 980, in __init__
File "C:\Python34\lib\site-packages\matplotlib\font_manager.py", line 1460, in findfont
File "C:\Python34\lib\site-packages\matplotlib\font_manager.py", line 1316, in findfont
File "c:\python\32-bit\3.4\lib\warnings.py", line 15, in showwarning
AttributeError: 'NoneType' object has no attribute 'write'