Bug 16805: Tweak new test message to say getalert

Bug 16805: Tweak new test message to say getalert

It said 'addalert', which is likely a cut-paste typo.
Plus, let's keep running the other tests if that one
goes bad.

TEST PLAN
---------
1) Apply Jonathan's test patch
2) prove t/db_dependent/Letters.t
   -- dies before finishing tests
3) Apply this test patch
4) prove t/db_dependent/Letters.t
   -- still dies before finished tests,
      'addalert' now is 'getalert' in message.
5) 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>