Remove useless "return null;" at the end of function block

program/lib/Roundcube/rcube.php

@@ -1489,8 +1489,6 @@ class rcube
         else if (isset($_SESSION['user_id'])) {
             return $_SESSION['user_id'];
         }
-
-        return null;
     }
 
     /**

program/lib/Roundcube/rcube_addressbook.php

@@ -360,7 +360,6 @@ abstract class rcube_addressbook
     function get_group($group_id)
     {
         /* empty for address books don't supporting groups */
-        return null;
     }
 
     /**

program/lib/Roundcube/rcube_image.php

@@ -82,8 +82,6 @@ class rcube_image
                 'channels' => $channels,
             );
         }
-
-        return null;
     }
 
     /**

program/lib/Roundcube/rcube_imap.php

@@ -2924,7 +2924,7 @@ class rcube_imap extends rcube_storage
     public function list_folders_subscribed_direct($root = '', $name = '*')
     {
         if (!$this->check_connection()) {
-           return null;
+            return null;
         }
 
         $config    = rcube::get_instance()->config;

program/lib/Roundcube/rcube_output.php

@@ -55,8 +55,6 @@ abstract class rcube_output
             case 'skins':   return $this->skins;
             case 'charset': return $this->charset;
         }
-
-        return null;
     }
 
     /**