Error while adding item to picklist. it Appeared today and worked perfectly before

Error while adding item to picklist. it Appeared today and worked perfectly before

Construction (ui.add) does not work since today. Errors: " Invalid client task found"


if(Invoice != Null)
{
for each  ServiceOrderRow in Service_Order[Invoice == input.Invoice]
{
input.Customer:ui.add(ServiceOrderRow.Customers);
}
input.Customer = ServiceOrderRow.Customers;
}