This throws an undefined index error for post_group -
PersonalMessage.template.php
// Show the member's avatar?
echo '
<a href="', $scripturl, '?action=profile;u=', $message['member']['id'], '" class="poster_avatar">';
if (!empty($settings['show_user_images']) && empty($options['show_no_avatars']) && !empty($message['member']['avatar']['image']))
{
echo '
', $message['member']['avatar']['image'], '</a>';
}
elseif (!empty($message['member']['group']))
{
echo '
<span class="no_avatar ', $message['member']['group'], '">', (substr($message['member']['name'], 0, 1)), '</span></a>';
}
elseif ($message['member']['post_group'] != '')
{
echo '
<span class="no_avatar ', $message['member']['post_group'], '">', (substr($message['member']['name'], 0, 1)), '</span></a>';
}
else
{
echo '
<span class="no_avatar">', (substr($message['member']['name'], 0, 1)), '</span></a>';
}