Bug 16805: Add test to getalert (no param passed)

Bug 16805: Add test to getalert (no param passed)

TEST PLAN
---------
1) apply patch
2) prove t/db_dependent/Letters.t
   -- fails
3) run koha qa test tools

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 5821ff3867c5291558238e54686c6834caa266c6)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
(cherry picked from commit a7dd3dcc3f565f18876f233cf8ade85cbc5b2d25)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>