If I ignored the error everything seemed to work fine.
Error
An error occurred. Please start Anki while holding down the shift key, which will temporarily disable the add-ons you have installed.
If the issue only occurs when add-ons are enabled, please use the Tools > Add-ons menu item to disable some add-ons and restart Anki, repeating until you discover the add-on that is causing the problem.
When you've discovered the add-on that is causing the problem, please report the issue on the add-on support site.
Debug info:
Anki 2.1.43 (0fbae6bc) Python 3.8.6 Qt 5.14.2 PyQt 5.14.2
Platform: Windows 10
Flags: frz=True ao=True sv=2
Add-ons, last update check: 2021-04-07 07:35:11
Caught exception:
Traceback (most recent call last):
File "aqt\webview.py", line 36, in cmd
File "aqt\webview.py", line 135, in _onCmd
File "aqt\webview.py", line 567, in _onBridgeCmd
AttributeError: 'NoneType' object has no attribute 'installEventFilter'