UDF are not populated when updated via API

Symptoms
UDF are not populated when updated via API.

Error messages/Warnings
API logs have the following error which indicates a problem with the UDF format:

"Error: -57"

The error means "UDF field format is not valid".

Reason
The XML sent to the server has extra LineFeed (LF) characters for the date configurable fields (UDF) which fails the update with the error above.

Resolution
Do not provide any value for empty UDF, e.g. do not use LF for the empty date fields.