declare custom exceptions as serializable

Author: vkovec

Packages/com.unity.formats.fbx/Editor/Scripts/ConvertToModel.cs

@@ -7,6 +7,7 @@
 
 namespace UnityEditor.Formats.Fbx.Exporter
 {
+    [System.Serializable]
     public class ConvertToLinkedPrefabException : System.Exception
     {
         public ConvertToLinkedPrefabException()

Packages/com.unity.formats.fbx/Editor/Scripts/FbxPrefabAutoUpdater.cs

@@ -504,6 +504,7 @@ public static void Append<K1, K2, V>(ref Dictionary<K1, Dictionary<K2, List<V>>>
             /// <summary>
             /// Exception that denotes a likely programming error.
             /// </summary>
+            [System.Serializable]
             public class FbxPrefabException : System.Exception
             {
                 public FbxPrefabException() { }