QFont::lastResortFont: Cannot find any reasonable font

While doing some exercises with QFont class, my program crashed with the following message: "QFont::lastResortFont: Cannot find any reasonable font".

The name of the font was supposed to be written in a label (code sample attached as a printscreen).

I checked the docs and saw a notice asking to report the bug, if it occurred.

Attached are the list of fonts on my system and a printscreen showing my code and the application output.