Fatal error: Uncaught Error: Call to undefined function wp_is_serving_rest_request() in /customers/e/4/f/opgendemke.be/httpd.www/wp-content/plugins/contact-form-7/includes/submission.php:54
Stack trace:
#0 /customers/e/4/f/opgendemke.be/httpd.www/wp-content/plugins/contact-form-7/includes/controller.php(17): WPCF7_Submission::is_restful()
#1 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/class-wp-hook.php(322): wpcf7_control_init()
#2 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#3 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/plugin.php(565): WP_Hook->do_action(Array)
#4 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/class-wp.php(418): do_action_ref_array('parse_request', Array)
#5 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/class-wp.php(813): WP->parse_request('')
#6 /customers/e/4/f/opgendemke.be/httpd.www/wp-includes/functions.php(1336): WP->main('')
#7 /customers/e/4/f/opgendemke.be/httpd.www/wp-blog-header.php(16): wp()
#8 /customers/e/4/f/opgendemke.be/httpd.www/index.php(17): require('/customers/e/4/...')
#9 {main}
  thrown in /customers/e/4/f/opgendemke.be/httpd.www/wp-content/plugins/contact-form-7/includes/submission.php on line 54