I'm getting this error in my WordPress dashboard which has to do with the custom post type I've got set up.

"Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'admin_init' not found or invalid function name in /nfs/c03/h01/mnt/81147/domains/bitthirsty.com/html/wp-includes/plugin.php on line 406"

This is how my custom post type is set up in functions.php file:

add_action('init', 'lists_register');

function lists_register() {

  $labels = array(
    'name' => _x('Lists', 'post type general name'),
    'singular_name' => _x('List', 'post type singular name'),
    'add_new' => _x('Add New', 'list item'),
    'add_new_item' => __('Add New List'),
    'edit_item' => __('Edit List'),
    'new_item' => __('New List'),
    'view_item' => __('View List'),
    'search_items' => __('Search Lists'),
    'not_found' =>  __('Nothing found'),
    'not_found_in_trash' => __('Nothing found in Trash'),
    'parent_item_colon' => ''
  );

  $args = array(
    'labels' => $labels,
    'public' => true,
    'publicly_queryable' => true,
    'show_ui' => true,
    'query_var' => true,
    'menu_icon' => get_stylesheet_directory_uri() . '/article16.png',
    'rewrite' => true,
    'capability_type' => 'post',
    'hierarchical' => false,
    'menu_position' => null,
    'supports' => array('title','editor','thumbnail')
    ); 

  register_post_type( 'lists' , $args );
  }

  add_action("admin_init", "admin_init");

  global $post;

  add_action('save_post', 'save_details');

Any idea what could be the problem?

Any help would be appreciated.

Thanks in advance!