Fixed - php notices on single ticket page

Need to use the ```init``` hook instead of ```after_setup_theme```,
otherwise you'll get on the single ticket page php notices like
following:
```Notice: Trying to get property of non-object in
/wp-includes/query.php on line 3516
Notice: Trying to get property of non-object in /wp-includes/query.php
on line 3521
Notice: Trying to get property of non-object in /wp-includes/query.php
on line 3530```