tests/valgrind: check QApplication::exec()
tests/valgrind: check QApplication::exec()

This probably should have been part of 5b538be6441a994dbd99ad157ea5186f0b09aecf.

Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui