fix: nil pointer dereference when selecting database

Prior to this commit the fact of selecting which redis database to dump when making use of the option `-db {redis_db}` would yield a nil pointer de-reference error due do the fact that a nil pointer can not be de-referenced even if it is an assignment expression.

Author: sonirico

main.go

@@ -103,7 +103,7 @@ func realMain() int {
 			return 1
 		}
 	} else {
-		var db *uint8 = nil
+		var db *uint8 = new(uint8)
 		if c.Db != -1 {
 			*db = uint8(c.Db)
 		}