Icon change

I am not able to change the menu icons. when I click on the select icon I get a blank list. I also tied to modify it manually in menu-link-4.php by changing the default property as this. it will always show ions-ios-meny
$wp_customize->add_setting( ‘mobile_menu_builder_customizer[menu-4-icon]’, array(
‘type’ => ‘option’,
‘capability’ => ‘edit_theme_options’,
‘transport’ => ‘postMessage’,
‘default’ => ‘ion-ios-phone-portrait’,
));