Prevent persisting shipment items before shipment has been saved to m…

…ake sure no orphan (shipment_id = 0) items exist in DB. Prevent reading items for shipments with empty id.

includes/wc-gzd-shipment-functions.php

@@ -461,7 +461,6 @@ function wc_gzd_create_shipment( $order_shipment, $args = array() ) {
 
 function wc_gzd_create_shipment_item( $shipment, $order_item, $args = array() ) {
 	try {
-
 		if ( ! $order_item || ! is_a( $order_item, 'WC_Order_Item' ) ) {
 			throw new Exception( _x( 'Invalid order item', 'shipments', 'woocommerce-germanized-shipments' ) );
 		}
@@ -471,8 +470,10 @@ function wc_gzd_create_shipment_item( $shipment, $order_item, $args = array() )
 		$item->set_order_item_id( $order_item->get_id() );
 		$item->set_shipment( $shipment );
 		$item->sync( $args );
-		$item->save();
 
+		if ( $shipment->get_id() > 0 ) {
+			$item->save();
+		}
 	} catch ( Exception $e ) {
 		return new WP_Error( 'error', $e->getMessage() );
 	}

src/DataStores/Shipment.php

@@ -559,6 +559,10 @@ protected function update_or_delete_meta( $object, $meta_key, $meta_value ) {
 	public function read_items( $shipment ) {
 		global $wpdb;
 
+		if ( $shipment->get_id() <= 0 ) {
+			return array();
+		}
+
 		// Get from cache if available.
 		$items = 0 < $shipment->get_id() ? wp_cache_get( 'shipment-items-' . $shipment->get_id(), 'shipments' ) : false;