fix external-URL handling and associated preference checkbox

svn: r1565

collects/browser/private/hyper.ss

@@ -853,7 +853,7 @@ A test case:
                        (lambda (new-url) (loop (- n 1) new-url))]
                       [else
                        (cons html-editor url)]))
-                  (cons #f #f))))))
+                  #f)))))
       
       (define hyper-canvas% (hyper-canvas-mixin canvas:basic%))
       

collects/help/private/main.ss

@@ -35,7 +35,7 @@
                 [cb (instantiate check-box% ()
                       (label (string-constant plt:hd:use-homebrew-browser))
                       (parent cbp)
-                      (value (preferences:get 'drscheme:help-desk:separate-browser))
+                      (value (not (preferences:get 'drscheme:help-desk:separate-browser)))
                       (callback
                        (lambda (cb evt)
                          (preferences:set 'drscheme:help-desk:separate-browser