bail out in case of missing descriptors
bail out in case of missing descriptors

Change-Id: I7c231367a4b5ef2d15fd1a7af2c2a6c1d51c9460
Reviewed-on: http://codereview.qt-project.org/6279
Sanity-Review: Qt Sanity Bot <5581206bb7e0307f0d99eb71898ae6b694149ca5@ovi.com>
Reviewed-by: Jonas Rabbe <6e9178b26dba0cd114a9aed0874c56cbbaba6438@nokia.com>
Reviewed-by: Michael Goddard <3ec82c9d770214b86c58e0ffe200ac64c3ff8da3@nokia.com>

nezticle/qtmultimedia,mer-qt/qtmultimedia,webOS-ports/qtmultimedia,sergiusens/qtmultimedia,webOS-ports/qtmultimedia,jfaust/qtmultimedia,nezticle/qtmultimedia,sergiusens/qtmultimedia,mer-qt/qtmultimedia,nezticle/qtmultimedia,sergiusens/qtmultimedia,sergiusens/qtmultimedia,sergiusens/qtmultimedia,nezticle/qtmultimedia,nezticle/qtmultimedia,mer-qt/qtmultimedia,webOS-ports/qtmultimedia,webOS-ports/qtmultimedia,mer-qt/qtmultimedia,jfaust/qtmultimedia,mer-qt/qtmultimedia,jfaust/qtmultimedia,jfaust/qtmultimedia,webOS-ports/qtmultimedia,jfaust/qtmultimedia