MDL-75719 completion: Fix viewed criteria.

When we unlock completion criteria and save changes 'viewed' criteria
still should be completed if user has viewed activity before. Seems
that that was broken by recent changes. Fixing here.

lib/completionlib.php

@@ -1116,6 +1116,9 @@ public function get_data($cm, $wholecourse = false, $userid = 0, $unused = null)
 
                 if (empty($data->coursemoduleid)) {
                     $cacheddata[$data->cmid] = $defaultdata;
+                    if ($data->viewed) {
+                        $cacheddata[$data->cmid]['viewed'] = $data->viewed;
+                    }
                     $cacheddata[$data->cmid]['coursemoduleid'] = $data->cmid;
                 } else {
                     unset($data->cmid);