Draft: Make IP and IPChi2 functors return optional
This partially addresses #542
(but only for IP and IPCHI2 functors)
Needed for Moore!2886, but can be tested/merged without.
Edited by Wouter Hulsbergen
This partially addresses #542
(but only for IP and IPCHI2 functors)
Needed for Moore!2886, but can be tested/merged without.