[Bugfix]

http://esotericsoftware.com/forum/viewtopic.php?f=7&t=3244
Handle DefaultSkin being null

spine-unity/Assets/spine-unity/Editor/SpineEditorUtilities.cs

@@ -410,6 +410,9 @@ public class SpineEditorUtilities : AssetPostprocessor {
 
 		if(skin == null)
 			skin = skeletonDataAsset.GetSkeletonData(true).DefaultSkin;
+			
+		if(skin == null)
+			skin = skeletonDataAsset.GetSkeletonData(true).Skins[0];
 
 		anim.Reset();