Update cmd/vanitySubdomains.go

Co-authored-by: Han Qiao <[email protected]>

cmd/vanitySubdomains.go

@@ -25,7 +25,7 @@ Usage of vanity subdomains and custom domains is mutually exclusive.`,
 			if !experimental {
 				return errors.New("must set the --experimental flag to run this command")
 			}
-			return nil
+			return cmd.Root().PersistentPreRunE(cmd, args)
 		},
 	}