correctly handle bottoming out document buffer

gem300.rkt

@@ -31,7 +31,8 @@
 
 (define (next-cmd)
   (define (iter depth)
-    (when (> depth 0)
+    (when (and (> depth 0)
+               (> (pipe-content-length document-buffer) 0))
       (let ()
         (displayln (read-line document-buffer))
         (iter (sub1 depth)))))

net.rkt

@@ -3,7 +3,7 @@
 (provide get)
 
 (require openssl)
-(require net/url)
+(require net/url-string)
 
 ;; sends a request to a gemini server, and returns the status, header,
 ;; and the input port for the rest of the body.