Need to access backend

I recently downloaded a TripAdvisor plugin. The plugin instructed I added the texted code-
add_filter( ‘widget_text’, ‘shortcode_unautop’); add_filter( ‘widget_text’, ‘do_shortcode’);
into the Theme Functions File.

Now my login attempt into my wp-admin comes up with –

add_filter( ‘widget_text’, ‘shortcode_unautop’); add_filter( ‘widget_text’, ‘do_shortcode’);
Warning: Cannot modify header information – headers already sent by (output started at /home/gandrew_oliver/deddog.com/wp-content/themes/risen/functions.php:2) in /home/gandrew_oliver/deddog.com/wp-includes/pluggable.php on line 896

So I cannot access my wordpress page because unable to login.