[Woo POS] [Barcodes] Ensure the cart is updated on a main thread after scanning (#15803)

Author: staskus

WooCommerce/Classes/POS/Models/PointOfSaleAggregateModel.swift

@@ -186,7 +186,8 @@ extension PointOfSaleAggregateModel {
 @available(iOS 17.0, *)
 extension PointOfSaleAggregateModel {
     func barcodeScanned(_ barcode: String) {
-        Task {
+        Task { @MainActor [weak self] in
+            guard let self else { return }
             let placeholderItemID = cart.addLoadingItem().id
 
             analytics.track(