Bug 42343: Prevent holds JS error when no holds exist

In the holds view, opening a record with no existing holds can leave
holdsQueueTable undefined while follow-up code still calls api() on it.

This triggers a Firefox console error:

  Uncaught (in promise) TypeError: can't access property "api", holdsQueueTable is undefined

Test plan:
1. Navigate to a title that has no existing holds.
2. Confirm no holdsQueueTable undefined error is logged.
3. Navigate to a title that has existing holds.
4. Confirm the holds queue still loads normally.
5. Confirm hold actions that refresh the queue still work as expected.

Sponsored-by: Koha-Suomi Oy

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jan Kissig <bibliothek@th-wildau.de>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>

koha-tmpl/intranet-tmpl/prog/js/holds.js

@@ -1847,7 +1847,7 @@ async function load_patron_holds_table(biblio_id, split_data) {
         },
         hold_table_settings
     );
-    holdsQueueTable.api().page(0).draw(false);
+
     // Clear selectedHolds on page load
     localStorage.removeItem("selectedHolds");
     $(table_id).on("draw.dt", function () {