git for-each-ref --start-after segfaults for the files backend using the GDK 'Gitlab Test' repository

Steps to reproduce:

gdk reset-data
cd repositories/@hashed/d4/73/d4735e3a265e16eee03f59718b9b5d03019c07d8b6c51f90da3a666eec13ab35.git
git for-each-ref --start-after=refs/heads/add-ipython-files --count=5

Simply running git for-each-ref with --start-after as either refs/heads or refs/tags doesn't segfault. Example attached: