- lcd4linux: fix shutdown w/o external display; thx to [MCP]

https://www.neutrino-images.de/board/ax-mutant-hd51-wwio-bre2ze4k-air-digital-zgemma-h7-f75/zgemma-h7c-fehler-beim-ausschalten-reboot-t6882.html#p37448

package/lcd4linux/files-skel/etc/init.d/lcd4linux

@@ -70,7 +70,10 @@ doStop() {
 }
 
 doOff() {
-	echo "LCD::backlight(0)" | $lcd4linux -i > /dev/null 2>&1
+	# /tmp/.lcd-* gets created by extdisplay script when a display was found
+	if [ -e /tmp/.lcd-* ]; then
+		echo "LCD::backlight(0)" | $lcd4linux -i > /dev/null 2>&1
+	fi
 }
 
 case "$1" in