Minor - fixing PHP warning.

main/inc/lib/display.lib.php

@@ -1389,12 +1389,15 @@ class Display
                     $session['coach'] = get_lang('GeneralCoach').': '.api_get_person_name($session_info['firstname'], $session_info['lastname']);
                 }
                 if (isset($session_info['duration']) && !empty($session_info['duration'])) {
-
                     $userDurationData = SessionManager::getUserSession(
                             api_get_user_id(),
                             $session_id
                     );
-                    $totalDuration = $session_info['duration'] + intval($userDurationData['duration']);
+                    $userDuration = 0;
+                    if (isset($userDurationData['duration'])) {
+                        $userDuration = intval($userDurationData['duration']);
+                    }
+                    $totalDuration = $session_info['duration'] + $userDuration;
 
                     $daysLeft = SessionManager::getDayLeftInSession(
                         $session_id,