Can't access wp-admin after WordPress Update

Hello, hope someone can help me out.. I received an email saying how my website was automatically updated to version 3.8.2

When I visit my site, everything looks fine, however I cannot access wp-admin to make further changes as I get a php error statement stating there’s a problem in my functions.php file and wp-includes/pluggable.php (<–not sure what that is).

Odd thing is I never made any changes to my functions.php file and was not a problem before the update since I was able to access wp-admin. Currently, I only have one script in functions.php file to add scripts to my header. My website is a child theme of twentythirteen. Could someone please let me know what my functions.php may be missing for the new version of WP, thank you!

<?php

add_action( 'wp_enqueue_scripts', 'ynem_enqueue_scripts' );

if( !function_exists( 'ynem_enqueue_scripts' ) ){

function ynem_enqueue_scripts() {

			wp_register_script( 'nivoslider',
					get_stylesheet_directory_uri()
					. '/js/jquery.nivo.slider.pack.js',
					 'jquery' );
			wp_enqueue_script( 'jquery' );
			wp_enqueue_script( 'nivoslider' );
			wp_enqueue_script(
		                          'custom-script',
		                         get_stylesheet_directory_uri() . '/js/nivoslider.js',
		                         array( 'jquery' )
	);
	wp_enqueue_style('nivoslider', get_stylesheet_directory_uri('stylesheet_directory').'/js/nivo-slider.css', false, '2.1');
	}
	add_theme_support('post-thumbnails');
add_image_size('nivothumb', 960, 320, true);
}
?>