Display: More improvements to serial calls.

Partially fixes the Samsung 240x320 version of SpongeBob Movie,
which does some weird serial calls at startup and in turn sometimes
boots up with a white screen.

src/javax/microedition/lcdui/Displayable.java

@@ -362,7 +362,7 @@ protected void _invalidate()
 		{
 			isValidating = true;
 
-			try { render(); } 
+			try { Mobile.getDisplay().callSerially(() -> { render(); }); }
 			finally { isValidating = false; }
 		}
 	}