Revert "Removing unused ErrNilInput"
Revert "Removing unused ErrNilInput"

This reverts commit 6a175843290d4cd005c4824aa4f50b9f96213f69.

MrStrong/Sia,johnathanhowell/Sia,NebulousLabs/Sia,ChrisSchinnerl/Sia,mnsl/Sia,mharkus/Sia,MrStrong/Sia,mharkus/Sia,rivine/rivine,Mingling94/Sia,NebulousLabs/Sia,rivine/rivine,mtlynch/Sia,mtlynch/Sia,ericflo/Sia,ChrisSchinnerl/Sia,mnsl/Sia,ericflo/Sia