Well the quick fix for this should be in PersonalMessages.subs.php, have not tried it yet
// If they have post by email enabled, override disallow_sendBody
if (!$maillist && !empty($modSettings['disallow_sendBody']))
$message = '';
require_once(SUBSDIR . '/Emailpost.subs.php');
pbe_prepare_text($message, $subject);
// If they have post by email enabled, override disallow_sendBody
if (!$maillist && !empty($modSettings['disallow_sendBody']))
{
$message = '';
censorText($subject);
}
else
{
require_once(SUBSDIR . '/Emailpost.subs.php');
pbe_prepare_text($message, $subject);
}
I'll also make an update to the class so it does not toss that error should it ever bet a blank message.