Report a bug can't deal with error confirmation requests

[hinerm]

It's possible for the post_bug.cgi script to throw an error:

  <div class="throw_error">
    It looks like you didn't come from the right page (you have no valid token for
    the <em>create_bug</em> action while processing the
    'post_bug.cgi' script). The reason could be one of:<br>
    <ul>
      <li>You clicked the "Back" button of your web browser after having successfully
      submitted changes, which is generally not a good idea (but harmless).</li>
      <li>You entered the URL in the address bar of your web browser directly,
      which should be safe.</li>
      <li>You clicked on a URL which redirected you here <b>without your consent</b>,
      in which case this action is much more critical.</li>
    </ul>
    Are you sure you want to commit these changes anyway? This may result in
    unexpected and undesired results.
  </div>

This isn't handled by Fiji, so it just makes users unable to report bugs via Fiji.

[ctrueden]

The long-term plan is to create a new issue reporting system, which interfaces with GitHub issues. See imagej/ImageJ#122.