Tidying/General quality of life updates

General quality of life updates:

- Ticket contact edit: 'No one' should be logged when ticket isn't associated with any contact, rather than a blank space; also fix email content
- Ticket portal/guest: Only show 'Assigned to' if someone is actually assigned
- Ticket tasks: Don't allow adding/modifying tasks for tickets in a resolved state
- Portal contacts: Properly align word 'Contacts' in a similar way all other page headings are aligned
- Client PDF export/handover: Now opens in a new self-closing window

guest_view_ticket.php

@@ -80,7 +80,7 @@ if ($ticket_row) {
                 <br>
                 <strong>Priority:</strong> <?php echo $ticket_priority ?>
                 <br>
-                <?php if (empty($ticket_closed_at)) { ?>
+                <?php if (!empty($ticket_assigned_to) && empty($ticket_closed_at)) { ?>
                     <strong>Assigned to: </strong> <?php echo $ticket_assigned_to ?>
                 <?php } ?>
             </p>