Fix deserialization errors preventing context menus to open

Not a proper fix but Mono runtime seems to silently ignore this error when clipboard contains garbage data.

Source/Editor/CustomEditors/CustomEditor.cs

@@ -616,7 +616,14 @@ namespace FlaxEditor.CustomEditors
             else
             {
                 // Default
-                obj = JsonConvert.DeserializeObject(text, TypeUtils.GetType(Values.Type), JsonSerializer.Settings);
+                try
+                {
+                    obj = JsonConvert.DeserializeObject(text, TypeUtils.GetType(Values.Type), JsonSerializer.Settings);
+                }
+                catch
+                {
+                    obj = null;
+                }
             }
 
             if (obj == null || Values.Type.IsInstanceOfType(obj))