Bug 14956: (followup) Fix birthday date validation in Opac

Bug 14956: (followup) Fix birthday date validation in Opac

To reproduce / test:

- In Opac: Go to 'your personal details'
- Enter a valid birtday date
- In Staff client: Go to Home > Patrons > Update patron records
  (Link on start page: Patrons requesting modification)
- Verify that the birtday date is correct
- Back in Opac, clear the birthday date, try to submit
  => Validation message appears
- Enter an invalid date (32/32/2999 or 00/00/0000), try to submit
  => Birthday date field is cleared, validation message appears.

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as advertised. Wrong today corrected

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>