Bug 32271: (QA follow-up) Correction to 'can_be_blank' logic

Bug 32271: (QA follow-up) Correction to 'can_be_blank' logic

The logic introducing the can_be_blank check into the monetary decimal
format check was flawed and meant we were no longer checking decimal
formatting in the majority of cases. This patch updates that so we pass
the unit tests and correctly check any value passed that's not an empty
string.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit c42725bab4f7f4dc360d9b4fe0417b8b3082d879)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>