Add Media is not adding media

After clicking “add media” in the Text Block or any Imaging, nothing happens. When I update with the code giving in the theme functions .php:
function modify_jquery() {
if (!is_admin()) {
wp_deregister_script(‘jquery’);
wp_register_script(‘jquery’, ‘https://code.jquery.com/jquery-1.11.3.min.js’);
wp_enqueue_script(‘jquery’);
}
}
add_action(‘init’, ‘modify_jquery’);

the page goes blank and get stuck at wp-admin/post.php?post=405&action=edit#

Same with using “Insert Theme Shortcode”, nothing happens
My theme is up-tp-date.

Please help, this is urgent – I need to post very soon. THANKS!