Fix sd subdirectory encoder position

Followup to 7e386c7

Marlin/src/lcd/ultralcd.cpp

@@ -4862,7 +4862,7 @@ void kill_screen(const char* lcd_msg) {
       encoderPosition = 2 * ENCODER_STEPS_PER_MENU_ITEM;
       screen_changed = true;
       #if ENABLED(DOGLCD)
-        first_page = false;
+        drawing_screen = false;
       #endif
       lcdDrawUpdate = LCDVIEW_CLEAR_CALL_REDRAW;
     }