4.6 update – can´t do anything anymore

Hi, when I want to log in to my website I always get the following message and nothing else happens 🙁

Warning: array_merge(): Argument #1 is not an array in /home/content/n3pnexwpnas02_data02/27/3523827/html/wp-includes/theme.php on line 1557

Warning: array_unique() expects parameter 1 to be array, null given in /home/content/n3pnexwpnas02_data02/27/3523827/html/wp-includes/theme.php on line 1557

Warning: Cannot modify header information – headers already sent by (output started at /home/content/n3pnexwpnas02_data02/27/3523827/html/wp-includes/theme.php:1557) in /home/content/n3pnexwpnas02_data02/27/3523827/html/wp-includes/pluggable.php on line 1174