fix: Handle empty MOS time string

About the Contributor

This pull request is posted on behalf of the BBC.

This is a: Bug fix / feature?

If a field containing a mosTime is present but an empty string (E.G. opTime in listMachInfo) then an exception is thrown.

Empty fields have the current time inserted like they would if the field was undefined

[X] PR is ready to be reviewed.
[X] The functionality has been tested by the author.
[X] Relevant unit tests has been added / updated.
[x] Relevant documentation (code comments, system documentation) has been added / updated.