fix: no warnings when a hotel has no 4-person price in the event price table

The hotels of an event price table are sorted by their 4-person room price
(rooms are keyed by pax). Hotels without one raised 'Undefined array key 4' /
'array offset on null' on every request; they now compare as '' like PHP 7.4
read the missing offset, so the order is unchanged.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/ep_products/Classes/Service/DateService.php

@@ -421,10 +421,12 @@ class DateService implements SingletonInterface
         // Sort by category
         foreach ($priceTable as $category => $rows)
         {
+            // The rooms are keyed by pax, so this compares the 4-person prices; hotels without
+            // one compare as '' (what PHP 7.4 read from the missing offset)
             uasort($rows, function ($a, $b) {
                 return strcmp(
-                    $a['rooms'][Hotel::CATEGORY_SUPER_DELUXE]['price'],
-                    $b['rooms'][Hotel::CATEGORY_SUPER_DELUXE]['price']
+                    $a['rooms'][Hotel::CATEGORY_SUPER_DELUXE]['price'] ?? '',
+                    $b['rooms'][Hotel::CATEGORY_SUPER_DELUXE]['price'] ?? ''
                 );
             });
             $priceTable[$category] = $rows;