hotfix for #470: datatables error on empty ticket list
hotfix for #470: datatables error on empty ticket list

handle the no tickets match query case with js rather than python for DataTables compatibility

rossp/django-helpdesk,rossp/django-helpdesk,mrkiwi-nz/django-helpdesk,gwasser/django-helpdesk,django-helpdesk/django-helpdesk,gwasser/django-helpdesk,mrkiwi-nz/django-helpdesk,django-helpdesk/django-helpdesk,mrkiwi-nz/django-helpdesk,gwasser/django-helpdesk,mrkiwi-nz/django-helpdesk,rossp/django-helpdesk,rossp/django-helpdesk,django-helpdesk/django-helpdesk,gwasser/django-helpdesk,django-helpdesk/django-helpdesk