Fix: export data - get_files function call of provider directed to locallib.

dta/classes/privacy/provider.php

@@ -149,12 +149,14 @@ class provider implements \core_privacy\local\metadata\provider,
         }
         $user = new \stdClass();
         $assign = $exportdata->get_assign();
+        $plugin = $assign->get_plugin_by_type('assignsubmission', 'file');
         $submission = $exportdata->get_pluginobject();
         error_log('Submission class type: ' . get_class($submission));
 
         error_log('class type >>> ');
         error_log(print_r(get_class($submission), true));
-        $files = (new self)->get_files($submission, $user);
+        // $files = (new self)->get_files($submission, $user);
+        $files = $plugin->get_files($exportdata->get_pluginobject(), $user);
         foreach ($files as $file) {
             $userid = $exportdata->get_pluginobject()->userid;
             $dtaresultsummary = DBUtils::getresultsummaryfromdatabase($assign->id, $submission->id);