PreflightCheck: do not check for primary mag & inconsistencies if system has no mag

src/modules/commander/PreflightCheck.cpp

@@ -717,6 +717,7 @@ bool preflightCheck(orb_advert_t *mavlink_log_pub, vehicle_status_s &status,
 			}
 		}
 
+		if (sys_has_mag == 1) {
 			/* check if the primary device is present */
 			if (!prime_found) {
 				if (reportFailures && !failed) {
@@ -732,6 +733,7 @@ bool preflightCheck(orb_advert_t *mavlink_log_pub, vehicle_status_s &status,
 				failed = true;
 			}
 		}
+	}
 
 	/* ---- ACCEL ---- */
 	if (checkSensors) {