Fix CS/phpstan error

phpstan.neon.dist

@@ -7,6 +7,7 @@ parameters:
 
     ignoreErrors:
         - '~class (GSSAPIContext|KRB5CCache)~'
+        - '~Function pam_chpass invoked with 3 parameters, 4-5 required~'
 
     scanFiles:
         - vendor/pear/pear-core-minimal/src/PEAR.php

program/lib/Roundcube/rcube_imap.php

@@ -460,7 +460,7 @@ class rcube_imap extends rcube_storage
      *
      * @param string $name Namespace array index: personal, other, shared, prefix
      *
-     * @return null|string|array Namespace data
+     * @return string|array|null Namespace data
      */
     public function get_namespace($name = null)
     {

program/lib/Roundcube/rcube_storage.php

@@ -335,7 +335,7 @@ abstract class rcube_storage
      *
      * @param string $name Namespace array index: personal, other, shared, prefix
      *
-     * @return null|string|array Namespace data
+     * @return string|array|null Namespace data
      */
     abstract public function get_namespace($name = null);