QtQuick.Dialogs FileDialog: don't go astray into resources on Android

Needed part of the same fix from QTBUG-36006.

Task-number: QTBUG-37741
Change-Id: I3bfe518dfdd6027bdb932c612d01b0c8d1753dad
Reviewed-by: Liang Qi <liang.qi@digia.com>