Bug 41510: Add test for effective_bookable with missing itemtype

- Add test case for the scenario where an item has no itemtype
  because both items.itype and biblioitems.itemtype are NULL
- Note: We must set biblioitems.itemtype to NULL before creating the
  item because Koha::Item->store() automatically populates itype from
  biblioitems.itemtype when itype is not set

Test plan:
- Apply this patch only
- Run: prove t/db_dependent/Koha/Item.t :: effective_bookable
- Verify test 6 FAILS with "Can't call method 'bookable' on an
  undefined value"
- Apply the follow-up patch
- Run the test again
- Verify all tests PASS

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@openfifth.co.uk>
(cherry picked from commit 26ffc16c38)
Signed-off-by: Jacob O'Mara <Jacob.omara@openfifth.co.uk>

t/db_dependent/Koha/Item.t

@@ -3869,7 +3869,7 @@ subtest 'effective_not_for_loan_status() tests' => sub {
 
 subtest 'effective_bookable() tests' => sub {
 
-    plan tests => 5;
+    plan tests => 7;
 
     $schema->storage->txn_begin;
 
@@ -3920,5 +3920,20 @@ subtest 'effective_bookable() tests' => sub {
         '->effective_bookable returns item specific bookable value when item bookable is defined'
     );
 
+    my $biblio_no_itype = $builder->build_sample_biblio;
+    $biblio_no_itype->biblioitem->set({ itemtype => undef })->store;
+    my $item_no_itype = $builder->build_sample_item({
+        biblionumber => $biblio_no_itype->biblionumber,
+        itype        => undef,
+    });
+    warning_like {
+        is(
+            $item_no_itype->effective_bookable, 0,
+            '->effective_bookable returns 0 when item has no itemtype and item bookable is undefined'
+        );
+    }
+    qr/item-level_itypes set but no itemtype set for item/,
+        'Warning raised for missing itemtype when item-level_itypes is set';
+
     $schema->storage->txn_rollback;
 };