Bug 16857 - patron-attr-types.tt: Get rid of warnings "Argument "" isn't numeric"

Bug 16857 - patron-attr-types.tt: Get rid of warnings "Argument "" isn't numeric"

To vrify:
- Go to Home > Administration > Patron attribute types
- Make sure you have some patron attribute types with no branches limitation
- For each attribute type you get a warning in intranet-error.log:
patron-attr-types.pl: Argument "" isn't numeric in numeric gt (>) at (...)/koha-tmpl/intranet-tmpl/prog/en/modules/admin/patron-attr-types.tt line 284.

To test:
- Appy patch
- Verify that warnings no longer appear in intranet-error.log

Signed-off-by: Srdjan <srdjan@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit abb7980004ad75de4a51d06815f5e98e1cbb0f6d)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>