When subclassing a native type, calling native members in `__init__` before
`super().__init__()` has been called could cause a crash. In this
situation, `self` in `mp_convert_member_lookup` is the
`native_base_init_wrapper_obj`. The check added in this commit ensures
that an `AttributeError` is raised before this happens, which is consistent
with other failed lookups.
Also fix a typo in a related comment.
Signed-off-by: Laurens Valk <laurens@pybricks.com>
9ca668f881