PhotoVideoControl.qml: check if camera captures video before telling it to do so

This allows recording video locally in QGC when the camera doesn't advertise
it is able to record the video by itself.

src/FlightMap/Widgets/PhotoVideoControl.qml

@@ -101,7 +101,7 @@ Rectangle {
 
     function toggleShooting() {
         console.log("toggleShooting", _anyVideoStreamAvailable)
-        if (_mavlinkCamera) {
+        if (_mavlinkCamera && _mavlinkCamera.capturesVideo) {
             if(_mavlinkCameraInVideoMode) {
                 _mavlinkCamera.toggleVideo()
             } else {