Fix empty warning dialog on missing font in project

BUG: 401903
2 jobs for Applications/18.12 in 8 minutes and 43 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #518
freebsd
freebsd stable-kf5-qt5 qt5.12

00:03:22

passed #517
linux stable-kf5-qt5 qt5.10

00:08:43

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