fix dict-empty?

closes PR 14075

racket/collects/racket/private/dict.rkt

@@ -288,7 +288,7 @@
       (loop))))
 
 (define (fallback-empty? d)
-  (if (dict-iterate-first d) #t #f))
+  (not (dict-iterate-first d)))
 
 (define (fallback-count d)
   (let loop ([n 0] [i (dict-iterate-first d)])

racket/collects/syntax/private/id-table.rkt

@@ -8,7 +8,7 @@
 ;; No-contract version.
 
 (define-struct id-table (hash phase))
-;; where hash maps symbol => (listof (cons identifier value))
+;; where hash maps symbol => (nonempty-listof (cons identifier value))
 ;;       phase is a phase-level (integer or #f)
 
 (define (make-id-table-hash-code identifier->symbol)