make-readtable: fix argument checking

racket/src/expander/read/readtable.rkt

@@ -51,7 +51,7 @@
         (raise-argument-error 'make-readtable "(or/c char? #f)" key))
       
       ;; Mode determines how the key is mapped
-      (when (null? args)
+      (when (null? (cdr args))
         (cond
          [key (raise-arguments-error 'make-readtable
                                      (string-append "expected 'terminating-macro, 'non-terminating-macro, 'dispatch-macro,"

racket/src/racket/src/startup.inc

@@ -52197,7 +52197,7 @@ static const char *startup_source =
 "(values))))"
 "(let-values((()"
 "(begin"
-"(if(null? args_1)"
+"(if(null?(cdr args_1))"
 "(let-values()"
 "(if key_0"
 "(let-values()"