Fix to recreating the stock summary view everytime

prs.classes/Entities/Stock/StockSummary.cs

@@ -150,7 +150,7 @@ namespace Comal.Classes
         {
             // 
             AddTable<ProductInstance>()
-                .AddConstant<object?>(x => x.Job.ID, null);
+                .AddConstant<object?>(x => x.Job.ID, Guid.Empty);
 
             // BOM
             AddTable<JobBillOfMaterialsItem>(new Filter<JobBillOfMaterialsItem>(x => x.Job.ID).IsNotEqualTo(Guid.Empty));