do not write sensor variable to env if sensor not found (#559)

general/package/ingenic-osdrv-t31/files/script/load_ingenic

@@ -33,9 +33,14 @@ else
     SENSOR_INFO=$(cat /proc/jz/sinfo/info)
     check_return "get sensor type"
     SENSOR=${SENSOR_INFO#*:}
+    if [ "sensor not found" = "$SENSOR" ]; then
+        unset SENSOR
+        fw_setenv sensor
+    else
         logger -s -p daemon.info -t ingenic "Get data from sinfo and set SENSOR as ${SENSOR}"
         fw_setenv sensor $SENSOR && logger -s -p daemon.info -t ingenic "Write detected ${SENSOR} to U-Boot ENV"
     fi
+fi
 
 
 case ${SENSOR} in