Prevent error by making sure the is_plugin_active_for_network function is loaded

woocommerce-basic-ordernumbers.php

@@ -20,6 +20,9 @@ if ( ! defined( 'ABSPATH' ) ) {
  * Check if WooCommerce is active
  **/
 function oton_is_wc_active() {
+	if ( ! function_exists( 'is_plugin_active_for_network' ) ) {
+		require_once( ABSPATH . '/wp-admin/includes/plugin.php' );
+	}
 	return 
 		in_array( 'woocommerce/woocommerce.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ) ) 
 		||