add an extra check to make sure drracket is more likely to startup when things go wrong in strange ways

Please merge to the 5.1 release branch
(cherry picked from commit 823b6629aa)

collects/drracket/private/module-language.rkt

@@ -82,7 +82,11 @@
             (set! sandbox (make-evaluator 'racket/base)))))
       
       (define/override (first-opened settings)
-        (define ns (get-ns (get-auto-text settings)))
+        (define ns (with-handlers ((exn:fail? (lambda (x) #f)))
+                     ;; get-ns can fail in all kinds of strange ways;
+                     ;; just give up if it does, since an error here
+                     ;; means drracket won't start up.
+                     (get-ns (get-auto-text settings))))
         (when ns (current-namespace ns)))
       
       (define/private (get-ns str)