Unload assets with asset manager instead of disposing them

core/src/com/me/brickbuster/state/FieldState.java

@@ -24,7 +24,7 @@ public abstract class FieldState extends State {
 	@Override
 	public void dispose() {
 		super.dispose();
-		textures.dispose();
+		game.assets.unload("textures.atlas");
 	}
 
 }