The parsers are taken from the [Uctags](https://github.com/universal-ctags/ctags) project, so the first thing to check is if the latest version of Uctags itself has the problem.
If it does then that project is where to fix it. When the problem is fixed in Uctags then swapping the parser included with Geany for the latest from Uctags is the fix for Geany. Thats not a job for the fainthearted though.