fallback to no banner if extwiki unavailable

src/extwiki-generic.rkt

@@ -85,6 +85,7 @@
 
 (define/memoize (get-redirect-content wikiname) #:hash hash
   (define wiki (hash-ref wikis-hash wikiname #f))
+  (with-handlers ([exn:fail:http-easy:timeout? (λ (e) #f)])
     (cond
       [wiki
        (define display-name (cadr wiki))
@@ -125,6 +126,6 @@
                         ,@(for/list ([error construct-errors])
                             `(li ,error)))
                       "")))]
-    [#t #f]))
+      [#t #f])))
 (module+ test
   (check-not-false ((get-redirect-content "gallowmere") "MediEvil Wiki")))