fix: add missing file extension when exporting excel file

components/ILIAS/Test/src/ExportImport/ResultsExportExcel.php

@@ -44,12 +44,16 @@ public function __construct(
         private readonly \ilLanguage $lng,
         private readonly \ilObjUser $current_user,
         private readonly \ilObjTest $test_obj,
-        private readonly string $filename = '',
+        private string $filename = '',
         private readonly bool $scoredonly = true,
     ) {
         $this->user_date_format = $this->current_user->getDateTimeFormat();
         $this->aggregated_data = $test_obj->getAggregatedResultsData();
         $this->worksheet = new \ilExcel();
+
+        if (!str_contains($this->filename, '.xlsx')) {
+            $this->filename .= '.xlsx';
+        }
     }
 
     public function withFilterByActiveId(int $active_id): self