Rover: Ignore MSG_POSITION_TARGET_GLOBAL_INT for now

APMrover2/GCS_Mavlink.cpp

@@ -598,6 +598,7 @@ bool GCS_MAVLINK::try_send_message(enum ap_message id)
     case MSG_OPTICAL_FLOW:
     case MSG_GIMBAL_REPORT:
     case MSG_RPM:
+    case MSG_POSITION_TARGET_GLOBAL_INT:
         break; // just here to prevent a warning
 
     }