gps failure has priority over engine falure, in case both fail make sure

that the gps failure mode does not turn on the engine

src/modules/commander/state_machine_helper.cpp

@@ -511,10 +511,10 @@ bool set_nav_state(struct vehicle_status_s *status, const bool data_link_loss_en
 		} else if (status->rc_signal_lost_cmd) {
 			status->nav_state = NAVIGATION_STATE_AUTO_RTGS; //XXX
 		/* Finished handling commands which have priority , now handle failures */
-		} else if (status->engine_failure) {
-			status->nav_state = NAVIGATION_STATE_AUTO_LANDENGFAIL;
 		} else if (status->gps_failure) {
 			status->nav_state = NAVIGATION_STATE_AUTO_LANDGPSFAIL;
+		} else if (status->engine_failure) {
+			status->nav_state = NAVIGATION_STATE_AUTO_LANDENGFAIL;
 		} else if (((status->data_link_lost && data_link_loss_enabled) && status->rc_signal_lost) ||
 		    (!data_link_loss_enabled && status->rc_signal_lost && mission_finished)) {
 			status->failsafe = true;

src/modules/fw_att_control/fw_att_control_main.cpp

@@ -893,8 +893,12 @@ FixedwingAttitudeControl::task_main()
 						}
 					}
 
-					/* throttle passed through */
-					_actuators.control[3] = (isfinite(throttle_sp)) ? throttle_sp : 0.0f;
+					/* throttle passed through if it is finite and if no engine failure was
+					 * detected */
+					_actuators.control[3] = (isfinite(throttle_sp) &&
+							!(_vehicle_status.engine_failure ||
+								_vehicle_status.engine_failure_cmd)) ?
+						throttle_sp : 0.0f;
 					if (!isfinite(throttle_sp)) {
 						if (_debug && loop_counter % 10 == 0) {
 							warnx("throttle_sp %.4f", (double)throttle_sp);