`write-request-line' always prints a path component.

* module/web/http.scm (write-request-line): Always write "/" when path
  is empty, regardless of query.
* test-suite/tests/web-http.test ("write-request-line"): Add test.

module/web/http.scm

@@ -1137,16 +1137,13 @@ three values: the method, the URI, and the version."
           (display host-port port)))))
   (let ((path (uri-path uri))
         (query (uri-query uri)))
-    (if (not (string-null? path))
+    (if (string-null? path)
+        (display "/" port)
         (display path port))
     (if query
         (begin
           (display "?" port)
-          (display query port)))
-    (if (and (string-null? path)
-             (not query))
-        ;; Make sure we display something.
-        (display "/" port)))
+          (display query port))))
   (display #\space port)
   (write-http-version version port)
   (display "\r\n" port))

test-suite/tests/web-http.test

@@ -173,6 +173,10 @@
                               (build-uri 'http
                                          #:path "/pub/WWW/TheProject.html")
                               (1 . 1))
+  (pass-if-write-request-line "GET /?foo HTTP/1.1"
+                              GET
+                              (build-uri 'http #:query "foo")
+                              (1 . 1))
   (pass-if-write-request-line "HEAD /etc/hosts?foo=bar HTTP/1.1"
                               HEAD
                               (build-uri 'http