PSYNC2: luaCreateFunction() should handle NULL client parameter.
PSYNC2: luaCreateFunction() should handle NULL client parameter.

See #4483. This is needed because luaCreateFunction() is now called
from RDB loading code outside a client context.

oranagra/redis,spinlock/redis,nnog/redis,charsyam/redis,Sciumo/redis,oranagra/redis,GitHubMota/redis,antirez/redis,ofirluzon/redis,yossigo/redis,yossigo/redis,PKRoma/redis,ctripcorp/redis,Sciumo/redis,soloestoy/redis,spinlock/redis,soveran/redis,ctripcorp/redis,ofirluzon/redis,soveran/redis,neomantra/redis,soveran/redis,soloestoy/redis,ctripcorp/redis,neomantra/redis,charsyam/redis,yossigo/redis,pmem/redis,ofirluzon/redis,charsyam/redis,neomantra/redis,neomantra/redis,oranagra/redis,rogerchina/redis,rogerchina/redis,oranagra/redis,pmem/redis,antirez/redis,PKRoma/redis,GitHubMota/redis,soloestoy/redis,rogerchina/redis,ctripcorp/redis,spinlock/redis,rogerchina/redis,nnog/redis,neomantra/redis,Sciumo/redis,pmem/redis,Sciumo/redis,nnog/redis,soloestoy/redis,soloestoy/redis,charsyam/redis,GitHubMota/redis,antirez/redis,soveran/redis,PKRoma/redis,yossigo/redis,antirez/redis,ofirluzon/redis,GitHubMota/redis,PKRoma/redis,PKRoma/redis,pmem/redis,oranagra/redis,yossigo/redis,charsyam/redis,ofirluzon/redis,nnog/redis,spinlock/redis