Ticket #31987: 31987.3.diff

wp-admin/css/customize-widgets.css

@@ -342 +342 @@
 #available-widgets {
         position: absolute;
         overflow: auto;
-        top: 46px;
+        top: 0;
         bottom: 0;
         left: -301px;
         width: 300px;
+        padding-top: 46px;
         margin: 0;
         z-index: 1;
         background: #fff !important;