QGuiApplication: Report default platform name before initialization

Calling this function before we had a QGuiApplication instance, would
return an empty string, even if QT_QPA_DEFAULT_PLATFORM_NAME was defined
at compile time. We now return the default platform name

[ChangeLog][QtGui][QGuiApplication] QGuiApplication::platformName
now reports the default platform name if QGuiApplication hasn't been
instantiated yet. It used to return an empty string.

Pick-to: 6.6 6.5
Change-Id: Iffe7cde8943ed2d186bc494d0920b9cf79389dd0
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

0 files changed, 0 insertions, 0 deletions