Customizer: Hide the transport list when it's empty, especially for screen readers.

Also prevent invalid markup for `.customize-section-description`.

Props valendesigns.
Fixes #32843.


git-svn-id: https://develop.svn.wordpress.org/trunk@33282 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/customize-controls.css

@@ -227,6 +227,18 @@ body {
 	background: #fff;
 }
 
+div.customize-section-description {
+	margin-top: 22px;
+}
+
+div.customize-section-description p:first-child {
+	margin-top: 0;
+}
+
+div.customize-section-description p:last-child {
+	margin-bottom: 0;
+}
+
 #customize-theme-controls .customize-themes-panel h3.customize-section-title:first-child {
 	border-bottom: 1px solid #ddd;
 	padding: 12px 12px 12px 12px;

src/wp-admin/css/customize-nav-menus.css

@@ -408,7 +408,6 @@
 .menu-item-depth-11 > .menu-item-bar { margin-right: 220px; }
 
 /* Submenu left margin. */
-/* @todo menu-item-transport seems entirely unused. */
 .menu-item-depth-0  .menu-item-transport { margin-left: 0;      }
 .menu-item-depth-1  .menu-item-transport { margin-left: -20px;  }
 .menu-item-depth-3  .menu-item-transport { margin-left: -60px;  }

src/wp-admin/css/nav-menus.css

@@ -531,6 +531,11 @@ li.menu-item.ui-sortable-helper .menu-item-transport .menu-item-bar {
 	margin-top: 13px;
 }
 
+/* Hide the transport list when it's empty */
+.menu-item .menu-item-transport:empty {
+	display: none;
+}
+
 /* WARNING: The factor of 30px is hardcoded into the nav-menus JavaScript. */
 .menu-item-depth-0 { margin-left: 0px; }
 .menu-item-depth-1 { margin-left: 30px; }

src/wp-includes/class-wp-customize-section.php

@@ -363,7 +363,9 @@ class WP_Customize_Section {
 						</h3>
 					</div>
 					<# if ( data.description ) { #>
-						<p class="description customize-section-description">{{{ data.description }}}</p>
+						<div class="description customize-section-description">
+							{{{ data.description }}}
+						</div>
 					<# } #>
 				</li>
 			</ul>