Until this is fixed, here is a workaround that I use until then. You need to change the function zeal_all_posts_array() in the Customizer.php file. It is not perfect but it does the job.
function zeal_all_posts_array() {
$posts = get_posts( array(
'post_type' => 'post',
'posts_per_page' => -1,
'post_status' => 'publish',
'orderby' => 'title',
'order' => 'ASC',
));
$pages = get_pages( array(
'post_type' => 'page',
'posts_per_page' => -1,
'post_status' => 'publish',
'orderby' => 'title',
'order' => 'ASC',
));
$posts_array = array();
$posts_array[ 'posts' ] = '[Posts]';
foreach ( $posts as $post ) :
if ( ! empty( $post->ID ) ) :
$posts_array[ $post->ID ] = $post->post_title;
endif;
endforeach;
$posts_array[ 'pages' ] = '[Pages]';
foreach ( $pages as $page ) :
if ( ! empty( $page->ID ) ) :
$posts_array[ $page->ID ] = $page->post_title;
endif;
endforeach;
return $posts_array;
}