lcdui: Canvas: Only do serviceRepaints if not painting the screen

Minor mistake here, as it would immediately return if a paint
call was NOT underway. It should only return immediately if there
IS a paint underway, or if the canvas is not being shown.

Fixes the Panasonic VS3 version of Sonic 1. Related to #10.

src/javax/microedition/lcdui/Canvas.java

@@ -208,7 +208,7 @@ public void repaint(int x, int y, int width, int height)
 	public void serviceRepaints() 
 	{
 		// TODO: Flesh this out properly, some games might need it.
-		if(!isShown() || !isPainting) { return; }
+		if(!isShown() || isPainting) { return; }
 
 		// Right now all this does is force a redraw, no queue consideration is made.
 		Mobile.getPlatform().flushGraphics(platformImage, 0, 0, width, height);