GenericPropertyDrawer cannot detect both the built-in property drawer and a user-written property drawer of a serializable type (a class with the [Serializable] attribute), and displays "No PropertyDrawer for type..." when drawn in a collection editor.

From what I can tell in the code, the built-in property drawer is not detected because serializable types are not considered as having it, and no custom property drawer is detected because only property drawers in the ScriptableObject-Architecture.Editor assembly are checked.

May be related to #7 and commit a31f77a.