Fix handling of file uploads

- allow upload of one file only.
- new submit does not load previously existing files.

Author: srobotta

classes/question/file.php

@@ -82,7 +82,11 @@ protected function question_survey_display($formdata, $descendantsdata, $blankqu
         $draftitemid = file_get_submitted_draft_itemid($elname);
         $component = 'mod_questionnaire';
         $options = $this->get_file_manager_option();
-        file_prepare_draft_area($draftitemid, $this->context->id, $component, 'file', $this->id, $options);
+        if ($draftitemid > 0) {
+            file_prepare_draft_area($draftitemid, $this->context->id, $component, 'file', $this->id, $options);
+        } else {
+            $draftitemid = file_get_unused_draft_itemid();
+        }
         // Filemanager form element implementation is far from optimal, we need to rework this if we ever fix it...
         require_once("$CFG->dirroot/lib/form/filemanager.php");
 

classes/responsetype/file.php

@@ -48,9 +48,11 @@ public static function answers_from_webform($responsedata, $question) {
             $files = $fs->get_area_files($question->context->id, 'mod_questionnaire', 'file', $question->id,
                 "itemid, filepath, filename",
                 false);
-            $file = reset($files);
-            $record->value = $file->get_id();
-            $answers[] = answer\answer::create_from_data($record);
+            if (!empty($files)) {
+                $file = reset($files);
+                $record->value = $file->get_id();
+                $answers[] = answer\answer::create_from_data($record);
+            }
         }
         return $answers;
     }