Redis GETRANGE returns an empty string for nonexistent keys

Discussed in https://github.com/redis/redis/discussions/11360

GETRANGE should return nil on missing keys, like GET does. This is a breaking change, so should be handled in v 8.0. @redis/core-team please respond if you disagree.

Comment From: enjoy-binbin

yes, i also think it should return nil on missing keys

and maybe we should also mention SUBSTR, it is the same as GETRANGE

Comment From: madolson

Makes sense to me.

Comment From: oranagra

approved in a core-team meeting as a change for redis 8.0