* 'location' field is now optional, if not filled it it will always
default to an empty string instead of null. This is required for the
new mode 'forward' that has no use for this field. If the field
is empty in any other mode like 'add' or 'replace', the entry
will be skiped by the logic.
Change-Id: Ia964c3bb272c9772c51b836ac2418ee4cd7b7f42