Fixed ReloadBaseTypes being called 2 times when entering play mode

[PierreGac]

It appears that when entering in playmode, the ReloadBaseTypes() is called 2 times: instance.ReloadBaseTypes() => when the instance is null a new one will be created. Inside the ctor, at the end, ReloadBaseTypes() is called first. Then called again by the returned instance (instance.ReloadBaseTypes(). This fix will avoid such thing to happen. The same issue occurs with EditorUtilities.ReloadDecoratorTypes but the previous fix cannot be applied (execution order is unclear)