If a user cannot access to list info page, error message will no longer be shown.  Instead, the user quietly redirected to home page.  This change deals with two cases:
  - If a user successfully subscribed to a list and it's private list, user would see rejection message, because they have not logged in.
  - User could know whether arbitrary list exists or not, because private list rejected them with the message different from non-existing list.

This may fix issue #193.