Merge branch 'client_delete_everything-does-not-delete-everything' into 'stable-3.1'

Check explicitly for session username, fixes #5389

See merge request ispconfig/ispconfig3!922

Author: Till Brehm

interface/lib/classes/db_mysql.inc.php

@@ -709,7 +709,7 @@ public function datalogSave($db_table, $action, $primary_field, $primary_id, $re
 
 		if($diff_num > 0) {
 			$diffstr = serialize($diffrec_full);
-			if(isset($_SESSION)) {
+			if(!empty($_SESSION['s']['user']['username'])) {
 				$username = $_SESSION['s']['user']['username'];
 			} else {
 				$username = 'admin';

server/lib/classes/db_mysql.inc.php

@@ -709,7 +709,7 @@ public function datalogSave($db_table, $action, $primary_field, $primary_id, $re
 
 		if($diff_num > 0) {
 			$diffstr = serialize($diffrec_full);
-			if(isset($_SESSION)) {
+			if(!empty($_SESSION['s']['user']['username'])) {
 				$username = $_SESSION['s']['user']['username'];
 			} else {
 				$username = 'admin';