 		{
 			// check if this tile has a cached shape
 			var cachedValue:ProjectedShape = _tileSRSToShapeCache.get(tile, getDestinationSRS());
-			if (cachedValue != null)
+			if (cachedValue)
 				return cachedValue;
 			
 			// we need to create the cached shape

			for (var i:int = 0; i < allTiles.length; i++)
			{
				var tile:WMSTile = allTiles[i];
				if (tile.bitmapData == null)
				{
					if (displayMissingImage.value == false)
						continue;
					tile.bitmapData = _missingImage.bitmapData;
				}

			var nasaService:OnEarthProvider = _service as OnEarthProvider;
			var style:String = styles.value;
			
			if (!nasaService)
				return;
			
			nasaService.changeStyleToMonth(style);
