Fonts broken at application startup

Loading application sometimes text is broken with random glyphs picked. Restarting the application fixes the issue. Issue is reproduced roughly on 3-5 starts of the application.

The testapplication contains large font that takes a lot of time to load. If this file is not included in the application the issue cannot be reproduced.

It is also tested that setting qsg_render_loop = basic the issue cannot be reproduced.

So the theory is that fonts are not ready before they are used due to long load time / race condition.