Menu icons are not displayed

I am not sure if this is a bug or I am missing something. Anyway, icons on toolbar work OK, while on menu bar they don't display at all.

I've tried explicitly set QtCore.Qt.AA_DontShowIconsInMenus to False as well as set IconVisibleInMenu to True, but it doesn't help.

It doesn't matter what icon theme is used (Adwaita, Breeze, GNOME, Mist) - they are all affected (Fedora 30: MATE & GNOME).

If I good remember, Qt 5.11 on Flatpak (KDE 5.11) on MATE on Fedora 30 is not affected, while Qt 5.12 on Flatpak (KDE 5.12) on MATE on Fedora 30 is affected.

Qt 5.9 on RHEL 7 (MATE) is not affected by this issue.

Originally, I hit this issue with Notepadqq 1.9.99.

Sample code:

https://pastebin.com/raw/v6e7SpfF