Bug 22025: Remove warnings when importing patrons

Bug 22025: Remove warnings when importing patrons

The following warning is raised when importing patrons
Argument "" isn't numeric in numeric eq (==) at /usr/share/perl5/DBIx/Class/Row.pm line 1018

if one of the following headers is passed but does not have a value:
 * privacy
 * privacy_guarantor_fines
 * privacy_guarantor_checkouts
 * anonymized

Test plan:
- Do not apply the patch
- Generated a csv file with at least one those headers
- Import it using the import_patrons.pl script (or using the GUI)
- Notice the warnings without the patch
- Apply the patch
- Confirm that the warnings do not longer appear

Signed-off-by: Magnus Enger <magnus@libriotech.no>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>