Fatal error: Uncaught Error: Call to undefined function add_filter() in /home/antenaserwis/public_html/satserwis/wp-content/plugins/jetpack/class.jetpack-twitter-cards.php:338
Stack trace:
#0 /home/antenaserwis/public_html/satserwis/wp-content/plugins/jetpack/class.jetpack-twitter-cards.php(348): Jetpack_Twitter_Cards::init()
#1 {main}
thrown in /home/antenaserwis/public_html/satserwis/wp-content/plugins/jetpack/class.jetpack-twitter-cards.php on line 338