adjustment to the new audio-player module of racket-audio

playlist.rkt

@@ -51,6 +51,14 @@
     (define/public (get-length) length)
     (define/public (get-id) my-id)
 
+    (define/public (booklet-file)
+      (let* ((dir (path-only file))
+             (booklet-file (build-path dir "booklet.pdf")))
+        booklet-file))
+    
+    (define/public (has-booklet?)
+        (file-exists? (send this booklet-file)))
+
     (define/public (track< t2)
       (if (string-ci<? album (send t2 get-album))
           #t