Wolfgang lives in a region which does not have internet access (or at least it is extremely expensive). In the past he would send updates for GAP about once a year or so. Usually he would come out with a new version of GAP soon after each new GIMP release, but not much changed between GIMP 2.6 and GIMP 2.8 (and ffmpeg finally started providing release versions) so GAP did not need updating (except for this Map Object problem).

I took the liberty of submitting a bug report (and patch). I hope you do not mind.

That's fine by me, Saul!

Thanks Saulgoode and Jontait2 for helping to sort this problem.