Update CCTiledMapLayer.m

Fixes possible divide by zero. If the layer has no tileset, the tex is nil and causes pixelsToPoints to be INF. This causes the contentSize to be INF, INF and prevents any further layers from being parsed.

Author: smklinger

cocos2d/CCTiledMapLayer.m

@@ -117,7 +117,7 @@ -(id) initWithTilesetInfo:(CCTiledMapTilesetInfo*)tilesetInfo layerInfo:(CCTiled
 		_mapTileSize = mapInfo.tileSize;
 		_layerOrientation = mapInfo.orientation;
 
-		CGFloat pixelsToPoints = 1.0/tex.contentScale;
+		CGFloat pixelsToPoints = tex ? 1.0/tex.contentScale : 1.0;
 
 		// offset (after layer orientation is set);
 		CGPoint offset = [self calculateLayerOffset:layerInfo.offset];