mod_compat_roles: Fix attempt to index a nil value #1847 permissions[] is not a map with role names as keys since 817bc9873fc2 but instead a level with host names were added. This was likely an oversight. Refactored towards railroad.

<tr>
  <th>What is {x} {op} {y}?</th><td>
    <input name="captcha_challenge" type="hidden" value="{challenge}">
    <input name="captcha_reply" pattern="[0-9]+" required type="number">
  </td></tr>