don't show themodule langauge opt-in buttons when we're not in the module language anymore

(this extra check is necessary because we might have moved languages between
    the time the timer is started and when it fires)

   closes PR 11705

   Please merge to the release 5.1 branch
(cherry picked from commit c119cef915)

collects/drracket/private/module-language-tools.rkt

@@ -100,7 +100,9 @@
               (unless timer
                 (set! timer (new timer% 
                                  [notify-callback
-                                  (λ () (move-to-new-language))]
+                                  (λ () 
+                                    (when in-module-language?
+                                      (move-to-new-language)))]
                                  [just-once? #t])))
               (send timer stop)
               (send timer start 200 #t)))))