It took me forever to find a solution to this. I thought I would release my code here for anyone that needs an answer to this question. I had to use two functions in order to solve the problem.
The first function replaces the blank label with to prevent the deletion of the menu item.
add_action('wp_update_nav_menu', 'blank_menu_items');
function blank_menu_items($nav_menu_selected_id) {
$navmenudata = json_decode(stripslashes($_POST['nav-menu-data']),true);
$k=0;
foreach((array) $navmenudata as $data){
if(
isset($data['name']) &&
isset($data['value']) &&
strpos($data['name'], 'menu-item-title') !==false
){
if(trim($data['value']) == ''){
$data['value'] = ' ';
$navmenudata[$k] = $data;
}
}
$k++;
}
if(isset($_POST['menu-item-title'])){
$k=0;
foreach($_POST['menu-item-title'] as $key => $value){
if(trim($value) == ''){
$value=" ";
$_POST['menu-item-title'][$key] = $value;
}
$k++;
}
}
}
This second function simply removes the when the menu is rendered.
add_filter('wp_nav_menu_objects', 'blank_menu_display', 10, 2);
function blank_menu_display( $items, $args ){
foreach( $items as &$item ) {
$item->title = str_replace(' ','',$item->title);
}
return $items;
}
These were the basic functions and I did not include the ACF code to make it easier to understand.