Use query.all() instead of query.get()

src/Bundle/ChillTaskBundle/Resources/views/SingleTask/Person/confirm_delete.html.twig

@@ -12,7 +12,7 @@
         'title'             : 'Remove task'|trans,
         'confirm_question'  : 'Are you sure you want to remove the task about "%name%" ?'|trans({ '%name%' : person.firstname ~ ' ' ~ person.lastname } ),
         'cancel_route'      : 'chill_task_singletask_list',
-        'cancel_parameters' : app.request.query.get('list_params', { } ),
+Use        'cancel_parameters' : app.request.query.all('list_params'),
         'form'              : delete_form
     } ) }}