merged from 14_STABLE - fixed warning in Activity report/Outline

mod/chat/lib.php

@@ -141,6 +141,7 @@ function chat_user_outline($course, $user, $mod, $chat) {
 /// $return->time = the time they did it
 /// $return->info = a short text description
 
+    $return = NULL;
     return $return;
 }
 

mod/wiki/lib.php

@@ -169,6 +169,7 @@ function wiki_get_participants($wikiid) {
 //in the instance, independient of his role (student, teacher, admin...)
 //See other modules as example.
 
+    $return = NULL;
     return false;
 }