Dbo Forms: correctly validate invalid dates and times
Whenever a user would insert an invalid date or time within a Wt Dbo form, the system would clear the value in fields and as long as the fields aren't required, validation would succeed.
This is due to
WTime::toString returning an empty string by default for invalid
WTime objects. This empty string would then get passed to the validator through the
validate functions of
We need to make the Dbo Forms system aware of this so that it can validate the values correctly.