Shows values for unknown flight mode

src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc

@@ -170,6 +170,7 @@ QString PX4FirmwarePlugin::flightMode(uint8_t base_mode, uint32_t custom_mode) c
 
         if (!found) {
             qWarning() << "Unknown flight mode" << custom_mode;
+            return tr("Unknown %1:%2").arg(base_mode).arg(custom_mode);
         }
     } else {
         qWarning() << "PX4 Flight Stack flight mode without custom mode enabled?";