QmlRunControlFactory: Cleaner canRun code

Fixed a bug where the case config->qtVersion == 0 was mishandled.

Change-Id: Ic11133bcfbe402e8f7a19b99b59161f8a913a2ab
Reviewed-on: http://codereview.qt.nokia.com/1779


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Christiaan Janssen <christiaan.janssen@nokia.com>