diff --git a/AssetStudioFBXWrapper/FbxExporterContext.cs b/AssetStudioFBXWrapper/FbxExporterContext.cs
index 375569e..24e24b5 100644
--- a/AssetStudioFBXWrapper/FbxExporterContext.cs
+++ b/AssetStudioFBXWrapper/FbxExporterContext.cs
@@ -210,8 +210,13 @@ namespace AssetStudio.FbxInterop
         private void ExportMesh(ImportedFrame rootFrame, List<ImportedMaterial> materialList, List<ImportedTexture> textureList, IntPtr frameNode, ImportedMesh importedMesh, bool exportSkins)
         {
             var boneList = importedMesh.BoneList;
-            var totalBoneCount = boneList.Count;
-            var hasBones = exportSkins && boneList != null && totalBoneCount > 0;
+            var totalBoneCount = 0;
+            var hasBones = false;
+            if (exportSkins && boneList?.Count > 0)
+            {
+                totalBoneCount = boneList.Count;
+                hasBones = true;
+            }
 
             var pClusterArray = IntPtr.Zero;
 
diff --git a/AssetStudioGUI/Studio.cs b/AssetStudioGUI/Studio.cs
index cf0ea4d..af3f2a9 100644
--- a/AssetStudioGUI/Studio.cs
+++ b/AssetStudioGUI/Studio.cs
@@ -76,7 +76,7 @@ namespace AssetStudioGUI
             return 0;
         }
 
-        private static int ExtractStreamFile(string extractPath,StreamFile[] fileList)
+        private static int ExtractStreamFile(string extractPath, StreamFile[] fileList)
         {
             int extractedCount = 0;
             foreach (var file in fileList)
@@ -328,7 +328,7 @@ namespace AssetStudioGUI
                         {
                             key = -1 - type.m_ScriptTypeIndex;
                         }
-                        items.Add(key, new TypeTreeItem(key, type.m_Nodes));
+                        items[key] = new TypeTreeItem(key, type.m_Nodes);
                     }
                     typeMap.Add(assetsFile.unityVersion, items);
                 }