[unity] Fixed texture preset not being applied when more atlas pages are added later. Fixed atlas page count not being updated immediately after change. Closes #2266.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs

@@ -634,6 +634,7 @@ namespace Spine.Unity.Editor {
 			atlasAsset.atlasFile = atlasText;
 
 			List<string> pageFiles = new List<string>();
+			atlasAsset.Clear(); // force reload
 			Atlas atlas = atlasAsset.GetAtlas(onlyMetaData: true);
 			if (atlas != null) {
 				foreach (AtlasPage page in atlas.Pages)