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Warning: include_once(): Failed opening '/var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-admin/includes/plugin.php' for inclusion (include_path='.:/opt/plesk/php/7.1/share/pear') in /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/integrations/class-wp-smush-gutenberg.php on line 148

Fatal error: Uncaught Error: Call to undefined function is_plugin_active() in /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/integrations/class-wp-smush-gutenberg.php:155 Stack trace: #0 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/integrations/class-wp-smush-gutenberg.php(31): WP_Smush_Gutenberg->check_for_gutenberg() #1 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/class-wp-smush-core.php(491): WP_Smush_Gutenberg->__construct() #2 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/class-wp-smush-core.php(441): WP_Smush_Core->load_gutenberg() #3 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-includes/class-wp-hook.php(286): WP_Smush_Core->load_libs('') #4 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #5 /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #6 /var/www/vhosts/sjerpbou in /var/www/vhosts/sjerpbouwtsites.nl/httpdocs/wp-content/plugins/wp-smushit/core/integrations/class-wp-smush-gutenberg.php on line 155