mercurial.el: don't raise an error from find-file-hook

find-file() shouldn't fail even if unreadable .hg directory is exists.
Not enabling hg-mode is sufficient for that senario.

contrib/mercurial.el

@@ -750,8 +750,9 b' Push changes G '
   (run-hooks 'hg-mode-hook))
 
 (defun hg-find-file-hook ()
+  (ignore-errors
   (when (hg-mode-line)
-    (hg-mode)))
+      (hg-mode))))
 
 (add-hook 'find-file-hooks 'hg-find-file-hook)