better warning logs on invalid atlas xmls

flixel/graphics/frames/FlxAtlasFrames.hx

@@ -244,13 +244,20 @@ class FlxAtlasFrames extends FlxFramesCollection
 		var frames:FlxAtlasFrames = FlxAtlasFrames.findFrame(graphic);
 		if (frames != null)
 			return frames;
-
-		if (graphic == null || xml == null)
+
+		final xmlData = xml.getFirstElement();
+		if (xmlData == null)
+		{
+			FlxG.log.warn('Invalid xml: $xml');
 			return null;
-
+		}
+
+		if (graphic == null)
+			return null;
+
 		frames = new FlxAtlasFrames(graphic);
-
-		var data:Access = new Access(xml.getXml().firstElement());
+		
+		var data:Access = new Access(xmlData);
 
 		for (texture in data.nodes.SubTexture)
 		{
@@ -323,15 +330,20 @@ class FlxAtlasFrames extends FlxFramesCollection
 		var frames = FlxAtlasFrames.findFrame(graphic);
 		if (frames != null)
 			return frames;
-
-		if (graphic == null || xml == null)
+
+		final xmlData = xml.getFirstElement();
+		if (xmlData == null)
+		{
+			FlxG.log.warn('Invalid xml: $xml');
 			return null;
-
+		}
+
+		if (graphic == null)
+			return null;
+
 		frames = new FlxAtlasFrames(graphic);
-
-		final data = xml.getXml();
-
-		for (sprite in data.firstElement().elements())
+
+		for (sprite in xmlData.elements())
 		{
 			var trimmed = (sprite.exists("oX") || sprite.exists("oY"));
 			var rotated = (sprite.exists("r") && sprite.get("r") == "y");

flixel/system/FlxAssets.hx

@@ -75,6 +75,11 @@ abstract FlxXmlAsset(OneOfTwo<Xml, String>) from Xml from String
 		return cast(this, Xml);
 	}
 
+	inline public function getFirstElement()
+	{
+		return getXml().getFirstElement();
+	}
+
 	static inline function fromPath<T>(path:String):Xml
 	{
 		return fromXmlString(Assets.getText(path));