As far as I understand there are no good way to handle data from sharepoint when fields are empty or unset.
This means that if I want to use Parse JSON, I would have to create these defaults by testing each field for empty(), this is not very effecitve and no-code.
if(empty(item()?['fieldname']), '', item()?['fieldname'])
Since the sharepoint connector knows the datatype of the list fields, I think it would be a good idea use this knowledge to set a datatype defaults (example: C# defaults value table) so we don't have to create these tests.