Similar to the fix in 6bf8e960fa ("pan/bi: Do helper termination
analysis on clauses")
Though apparently a "theoretical issue only", fixes artefacts in
DarkPlaces with both D3D9 and GL renderers.
Fixes: 9a7f0e268b ("pan/mdg: Use the helper invo analyze passes")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12156>