Fix regression where creation of default folders wasn't functioning without prefix (#5460)

CHANGELOG

@@ -47,6 +47,7 @@ CHANGELOG Roundcube Webmail
 - Control search engine crawlers via X-Robots-Tag header instead of <meta> and robots.txt (#5098)
 - Fix bug where folders list would scroll to top when clicking on subscription checkbox (#5447)
 - Fix decoding of GB2312/GBK text when iconv is not installed (#5448)
+- Fix regression where creation of default folders wasn't functioning without prefix (#5460)
 
 RELEASE 1.2.2
 -------------

program/lib/Roundcube/rcube_imap.php

@@ -456,6 +456,11 @@ class rcube_imap extends rcube_storage
         $ns = $this->namespace;
 
         if ($name) {
+            // an alias for BC
+            if ($name == 'prefix') {
+                $name = 'prefix_in';
+            }
+
             return isset($ns[$name]) ? $ns[$name] : null;
         }