Problem with Delete action in Workflows / Rules

Hi,

When I delete an invoice, I'm trying to get his Sales Order Id to update a field on the Sales Order related to that invoice, but the fact is that the Delete action enables me to get that ID when I send an email or via webhook, but not in a custom function.

There's any way to solve this?

My code is like:

salesId = zoho.crm.getRecordById("Invoices", input.invoiceId);

id = salesId.get("Sales Order");

field = salesId.get("Billing");

updating = Map();

updating.put("Updated field", field);

update = zoho.crm.updateRecord("SalesOrders", id, updating);

When I try to get the id variable, returns null.

Any idea?

Thank you