The following code around line 377 in theme-parser.c looks wrong:

  retval = TRUE;

  n_attrs = 1;
  attrs[0].name = first_attribute_name;
  attrs[0].retloc = first_attribute_retloc;
  *first_attribute_retloc = NULL;

  va_start (args, first_attribute_retloc);

  name = va_arg (args, const char*);
  retloc = va_arg (args, const char**);

  while (name != NULL)
    {
      g_return_val_if_fail (retloc != NULL, FALSE);

      g_assert (n_attrs < MAX_ATTRS);

      attrs[n_attrs].name = name;
      attrs[n_attrs].retloc = retloc;
      n_attrs += 1;
      *retloc = NULL;

      name = va_arg (args, const char*);
      retloc = va_arg (args, const char**);
    }

  va_end (args);

  if (!retval)
    return retval;

retval can never be FALSE here.