Issue 5549 - Implement missing error handlings for custom filter lists

skin/desktop-options.css

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 1140 matching lines @@
 #all-filter-lists-table
 {
   margin-bottom: 0.8rem;
 }
 
 #custom-filters-edit
 {
   white-space: nowrap;
 }
 
-#custom-filters-edit-area
+#custom-filters-control
 {
   display: flex;
   width: 100%;
 }
 
 /*
   avoid doubled margin glitchy behavior
   as shown in visual specifications
 */
-#custom-filters-edit-area .side-controls .side-controls
+#custom-filters-control .side-controls .side-controls
 {
   margin: 0;
 }
 
 /*
   visibility: hidden;
   preserves the flex-box meaning,
   keeping buttons on the right.
 */
 #custom-filters-edit-error
@@ skipping 393 matching lines @@
   font-size: 1rem;
   color: #077CA6;
   background-color: #E1F2FA;
 }
 
 #notification strong
 {
   flex: 1;
   text-align: center;
 }