A code path asserted that the archiver was dead, but a check made that
impossible to happen.

Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACW=CYE1ars+2XyPTEPq0wQvru4c0dPZ=Nrn3EqNBkksvQ@mail.gmail.com
Backpatch-throgh: 14