QAPISchemaObjectType.check() does nothing for types that have been
checked already. Except the "has been checked" predicate is broken
for empty types: self.members is [] then, which isn't true. The bug
is harmless, but fix it anyway: use self.member is not None instead.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190914153506.2151-18-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>