[unity] Fixed automatic partial re-import when atlas png texture and/or material have been deleted and re-exported. Closes #1650.

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

@@ -349,6 +349,8 @@ namespace Spine.Unity.Editor {
 				}
 			}
 
+			AddDependentAtlasIfImageChanged(atlasPaths, imagePaths);
+
 			// Import atlases first.
 			var newAtlases = new List<AtlasAssetBase>();
 			foreach (string ap in atlasPaths) {
@@ -453,6 +455,18 @@ namespace Spine.Unity.Editor {
 			}
 		}
 
+		static void AddDependentAtlasIfImageChanged (List<string> atlasPaths, List<string> imagePaths) {
+			foreach (var imagePath in imagePaths) {
+				string atlasPath = imagePath.Replace(".png", ".atlas.txt");
+				if (!System.IO.File.Exists(atlasPath))
+					continue;
+
+				if (!atlasPaths.Contains(atlasPath)) {
+					atlasPaths.Add(atlasPath);
+				}
+			}
+		}
+
 		static void AddDependentSkeletonIfAtlasChanged (List<PathAndProblemInfo> skeletonPaths, List<string> atlasPaths) {
 			foreach (var atlasPath in atlasPaths) {
 				string skeletonPathJson = atlasPath.Replace(".atlas.txt", ".json");