Fix handling of special chars in ACL LOAD.
Fix handling of special chars in ACL LOAD.

Now it is also possible for ACL SETUSER to accept empty strings
as valid operations (doing nothing), so for instance

    ACL SETUSER myuser ""

Will have just the effect of creating a user in the default state.

This should fix #7329.

charsyam/redis,soloestoy/redis,PKRoma/redis,charsyam/redis,ofirluzon/redis,oranagra/redis,charsyam/redis,antirez/redis,neomantra/redis,ctripcorp/redis,neomantra/redis,soloestoy/redis,ofirluzon/redis,yossigo/redis,yossigo/redis,PKRoma/redis,charsyam/redis,ctripcorp/redis,neomantra/redis,ofirluzon/redis,PKRoma/redis,oranagra/redis,yossigo/redis,ofirluzon/redis,antirez/redis,ctripcorp/redis,ctripcorp/redis,soloestoy/redis,neomantra/redis,PKRoma/redis,soloestoy/redis,ofirluzon/redis,yossigo/redis,oranagra/redis,neomantra/redis,PKRoma/redis,antirez/redis,charsyam/redis,antirez/redis,yossigo/redis,oranagra/redis,soloestoy/redis,oranagra/redis