I think this should be `$hookData->pull_request->number`, same in line [#148](https://github.com/joomla/jissues/pull/282/files#diff-7136aadbd04e6f862c5c24cc6bb0dfaeR148) and [#174](https://github.com/joomla/jissues/pull/282/files#diff-7136aadbd04e6f862c5c24cc6bb0dfaeR174)