Use action=add-folder when creating a new folder

program/js/app.js

@@ -7355,7 +7355,8 @@ function rcube_webmail()
   this.show_folder = function(folder, path, force)
   {
     var win, target = window,
-      url = '&_action=edit-folder&_mbox='+urlencode(folder);
+      action = folder === '' ? 'add' : 'edit',
+      url = '&_action=' + action + '-folder&_mbox=' + urlencode(folder);
 
     if (path)
       url += '&_path='+urlencode(path);

program/steps/settings/func.inc

@@ -40,6 +40,7 @@ $RCMAIL->register_action_map(array(
     'unsubscribe'   => 'folders.inc',
     'purge'         => 'folders.inc',
     'folder-size'   => 'folders.inc',
+    'add-folder'    => 'edit_folder.inc',
     'add-identity'  => 'edit_identity.inc',
     'add-response'  => 'edit_response.inc',
     'save-response' => 'edit_response.inc',