QSqlDatabase uses a Q_APPLICATION_GLOBAL and so should not be used
without QCoreApplication instance. The test crashes if the existence
of an application instance is asserted in Q_APPLICATION_GLOBAL
code.
Pick-to: 6.6
Change-Id: Iaa3f4dff7b2722257735680dd3885aeed0ac810b
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>