While no negative consequences are currently known, it's clearly wrong
to not reset the context in one of the branches.

Reported-By: Dmitry Dolgov
Author: Dmitry Dolgov
Discussion: https://postgr.es/m/CAGPqQf165-=+Drw3Voim7M5EjHT1zwPF9BQRjLFQzCzYnNZEiQ@mail.gmail.com
Backpatch: 11-, where JIT compilation support was added