Fix XXX in less

customize.dist/src/less2/include/leftside-menu.less

@@ -2,11 +2,6 @@
 @import (reference) "./variables.less";
 @import (reference) "./colortheme-all.less";
 
-.leftside-menu_main() {
-    div.cp-empty-rule {
-        display: block; // XXX workaround lesshint complaining about empty rules
-    }
-}
 .leftside-menu-category_main() {
     .unselectable_make();
     padding: 5px 15px;