It's possible to come across TYPE_CODE_UNDEF at this point in
read_member_functions, which according to a comment in read_type
is used for forward references.
gdb/ChangeLog:
2020-10-22  Hannes Domani  <ssbssa@yahoo.de>
	* stabsread.c (read_member_functions): Remove gdb_assert.
+2020-10-22  Hannes Domani  <ssbssa@yahoo.de>
+
+       * stabsread.c (read_member_functions): Remove gdb_assert.
+
 2020-10-22  Hannes Domani  <ssbssa@yahoo.de>
 
        * gdbtypes.c (init_complex_type): Check target type name.
 
          /* These are methods, not functions.  */
          if (new_sublist->fn_field.type->code () == TYPE_CODE_FUNC)
            new_sublist->fn_field.type->set_code (TYPE_CODE_METHOD);
-         else
-           gdb_assert (new_sublist->fn_field.type->code ()
-                       == TYPE_CODE_METHOD);
 
          /* If this is just a stub, then we don't have the real name here.  */
          if (new_sublist->fn_field.type->is_stub ())