Error when using modified Theme

I used to have a line in my Template as a ‘footer’, where the Template started with:

and ended with:

[code]< table style=“width: 100%; position: absolute; bottom: 0px; left: 0px; right: 0px”>

Graag betaling onder vermelding van factuur {{ reference }} van {{ issue_date | date_to_string }} binnen 5 werkdagen op bankrekening ... ten name van ... [/code]

But now with the new Themes it does not work any more and I get the message:
When sending an email from Sales Invoices I get the error:

NullReferenceException: De objectverwijzing is niet op een exemplaar van een object ingesteld.

Or when creating a PDF from Sales Invoices I get the error:

bij ManagerServer.PdfConverter.ConvertHtmlToPdf(String input, Stream output, PageBoundary pageBoundary)
bij ManagerServer.HttpHandlers.Pdf.Post()```

What is wrong? Can I no longer use:
[code]{{ issue_date | date_to_string }}[/code]

Thanks for support!

Do the other templates still work? I don’t see anything wrong with your code that could cause this issue.

I do not know for a fact that this is the problem, but I believe Manager’s Liquid templating engine does not support all substitution filters. So your date_to_string operation could be the problem. Try leaving that out and see if things work.