issue: Queue Sort Title No Validation Error

This addresses an issue reported on the Forum where adding a new Sort Option
for Queues without a title fails without error. This is due to the
queue-sorting template that uses a new instance of the
`QueueSortDataConfigForm` form from a new instance of `QueueSort` rather
than the existing form with existing POST data/errors when a POST is
submitted. This updates the queue-sorting template to use the already
available `$data_form` form instance. This also adds an if statement to set
the `$data_form` if one doesn’t exist (this only applies to new modals
without a POST).