Ticket #38951: 38951.1.diff

src/wp-content/themes/twentyseventeen/assets/js/customize-preview.js

@@ -8 +8 @@
 
         // Collect information from customize-controls.js about which panels are opening.
         wp.customize.bind( 'preview-ready', function() {
+                
+                // Initially hide the theme option placeholders on load
+                $( '.panel-placeholder' ).hide();
+                
                 wp.customize.preview.bind( 'section-highlight', function( data ) {
 
                         // Only on the front page.