QTfrontend: Fix flickering and bad offset of control config popup
If you opened the pop-up to change a key, there was a very short flicker at the left side
and the pop-up had a bad offset which sometimes caused entries to be out of screen bounds.
AAAAaXicAWkAlv8ITgKBAAmqA0YACZMErAAISQV1AAbfBXoABZEEsAAFVQM9AAbWAoYAB5cAqpkHlwc7AAMmA/WZDB4D9QADtAEBmQtiBvIAA7kHCZkLawD8AA2jAaaFDboGDYUBhQYthQGPAlSFB6AEC/E0HxtP