Add explicit instanceof check in batch() to prevent fatal error on get_id()

Author: layoutd

includes/Generator/Order.php

@@ -253,7 +253,7 @@ public static function batch( $amount, array $args = array() ) {
 
 		for ( $i = 1; $i <= $amount; $i ++ ) {
 			$order = self::generate( true, $args );
-			if ( ! $order ) {
+			if ( ! $order instanceof \WC_Order ) {
 				error_log( "Batch generation failed: Order {$i} of {$amount} could not be generated" );
 				continue;
 			}