Import 8405a40ae9: Fixed window centering on macOS (by Maki)

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This is an automated proposal to look at a commit made by Maki and import it into Overte

Commit:	8405a40ae96694b9a513319cae57fa7584643d36
Author:	Maki
Date:	Tue, 21 Apr 2020 22:56

Fixed window centering on macOS

Stats:

Filename	Stats	Lines	Added	Removed	Lines in blame
libraries/ui/src/MainWindow.cpp		24	15	9	14
1 files	-	24	15	9	14

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