[unity] Fixed Leftover AnimationState applied when calling Initialize(true). Closes #2475.

spine-unity/Assets/Spine/Runtime/spine-unity/Components/SkeletonAnimation.cs

@@ -184,6 +184,7 @@ namespace Spine.Unity {
 			if (BuildUtilities.IsInSkeletonAssetBuildPreProcessing)
 				return;
 #endif
+			state = null; // prevent applying leftover AnimationState
 			base.Initialize(overwrite, quiet);
 
 			if (!valid)