If you've updated YITH WooCommerce Wishlist plugin to the newest 2.2.0 version, it's possible that your site is broke (especially if WP_DEBUG is enabled).
In that case, please do the following:
1. Locate 237 line in yit-debug.php (located in \wp-content\plugins\yith-woocommerce-wishlist\plugin-fw\lib folder on your server):
$plugin_fw_version = get_file_data( trailingslashit( YIT_CORE_PLUGIN_PATH ) . 'init.php', array( 'Version' => 'Version' ) )[ 'Version' ];
2. Replace it with:
$plugin_fw_version = get_file_data( trailingslashit( YIT_CORE_PLUGIN_PATH ) . 'init.php', array( 'Version' => 'Version' ) );
3. Save!