ASSERT: "mask.width() <= c.w && mask.height() <= c.h" in file painting\qtextureglyphcache.cpp, line 321

Getting this error sometimes on application startup. It's intermittent, and I can't figure out what triggers it. Been getting this error on and off on different machines at different times during the last one year at least, maybe two, but never before. Only happens in debug build, which is a poor consolation when I actually need to debug my application.

One thing it certainly isn't tied to is my source code - the very same code revision sometimes fails and sometimes succeeds, on the same machine.

Here's the actual assertion (full screenshot in the attachments):

Here's the complete call stack:

Here's the project where I'm getting this error: https://github.com/VioletGiraffe/file-commander

Built with Qt 5.12.4 / 5.13.0 msvc2017_64.

The assert cannot be ignored, the program simply crashes. Here's what happens when I launch the program:

1. I see a window with proper title and borders, but blank (white) contents.
2. Aforementioned assertion.
3. The window gets fully painted in the background underneath the assertion message box.
4. Second instance of the same assertion.
5. Crash as soon as I click "Ignore".

Any advice on how to circumvent the crash is very welcome.