Pipeline error when date field is empty and using {{datefield|date_dmy}} to format date

I have a pipeline that takes several date fields and writes them out to text fields in another table, with {{datefield|date_dmy}} used to format the date. It works when all the date fields contain a date, but fails when any of the fields are empty, producing an error 'Validation error: Incorrect template'. 

Has anyone else had the same issue and/or know how to workaround this without adding in conditions to check for fields being blank (as this isn't a feasible solution) or creating formula fields in the table to format the dates as strings? 

Thanks.

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Jeremy Anson
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