amxhooks: Don't write to *retval in amx_Exec() if badRetVal isn't set
amxhooks: Don't write to *retval in amx_Exec() if badRetVal isn't set

Zeex/sampgdk,WopsS/sampgdk,WopsS/sampgdk,Zeex/sampgdk,WopsS/sampgdk,Zeex/sampgdk