- Fix "PHP Warning: Invalid argument supplied for foreach()" (#1488264)

program/steps/settings/folders.inc

@@ -293,6 +293,7 @@ function rcube_subscription_form($attrib)
         if (!$disabled && $folder['virtual'] && $folder['level'] == 0 && !empty($namespace)) {
             $fname = $folder['id'] . $delimiter;
             foreach ($namespace as $ns) {
+                if (is_array($ns)) {
                     foreach ($ns as $item) {
                         if ($item[0] === $fname) {
                             $disabled = true;
@@ -301,6 +302,7 @@ function rcube_subscription_form($attrib)
                     }
                 }
             }
+        }
         // check if the folder is an other users virtual-root folder, then disable subscription option on it
         if (!$disabled && $folder['virtual'] && $folder['level'] == 1
             && !empty($namespace) && !empty($namespace['other'])