Userportal: Fix coach url when it is null - refs BT#21436

main/inc/lib/userportal.lib.php

@@ -2050,9 +2050,14 @@ class IndexManager
                                 $params['category_id'] = $session_box['category_id'];
                                 $params['title'] = $session_box['title'];
                                 $params['id_coach'] = $coachId;
-                                $userIdHash = UserManager::generateUserHash($coachId);
-                                $params['coach_url'] = api_get_path(WEB_AJAX_PATH).
-                                    'user_manager.ajax.php?a=get_user_popup&hash='.$userIdHash;
+                                $params['coach_url'] = '';
+
+                                if ($coachId) {
+                                    $userIdHash = UserManager::generateUserHash($coachId);
+                                    $params['coach_url'] = api_get_path(WEB_AJAX_PATH).
+                                        'user_manager.ajax.php?a=get_user_popup&hash='.$userIdHash;
+                                }
+
                                 $params['coach_name'] = !empty($session_box['coach']) ? $session_box['coach'] : null;
                                 $params['coach_avatar'] = UserManager::getUserPicture(
                                     $coachId,