Uninitialized value in addition (+) at SL/IS.pm

[sse450]

Use of uninitialized value in addition (+) at SL/IS.pm line 1280.
Use of uninitialized value in addition (+) at SL/IS.pm line 1281.
Set-Cookie: SL-mufit_onart2024=m27642uf0a_7t11n277roi260t149; expires=Tue, 26-May-2026 08:12:06 GMT; path=/; Content-Type: text/html

This happens on Sales Invoice record page. Besides the above error, sales invoice doesn't record the invoice total.
Please note:

1. The currency is not base currency. But the exchange rate is on file.
2. The product is an assembly and on stock.
3. Line total is correct
4. However, when I get a report from Account Receivables | Reports | Trasactions, I cannot see the total invoice value on the report.values for these two invoices are correctly shown. But the one with assembly total is empty in total.
5. Balance for that company is also wrong as it omits the invoice with assembly.

Perhaps, the above reported "uninitialized value" causes this. IDK.