Fix M0 unused var warning

Marlin/src/gcode/lcd/M0_M1.cpp

 
   planner.synchronize();
 
-  const bool seenQ = parser.seen('Q');
-  #if HAS_LEDS_OFF_FLAG
-    if (seenQ) printerEventLEDs.onPrintCompleted();      // Change LED color for Print Completed
+  #if HAS_LCD_MENU || HAS_LEDS_OFF_FLAG
+    const bool seenQ = parser.seen('Q');
+    #if HAS_LEDS_OFF_FLAG
+      if (seenQ) printerEventLEDs.onPrintCompleted();  // Change LED color for Print Completed
+    #endif
   #endif
 
   #if HAS_LCD_MENU