https://bugs.winehq.org/show_bug.cgi?id=54144
--- Comment #2 from Esme Povirk madewokherd@gmail.com --- cominterop_get_interface is called with a NULL MonoClass. I think that when an object type field has UnmanagedType.Interface marshaling, mono_cominterop_emit_object_to_ptr_conv tries to marshal it as a class but can't get a type for the interface.