Bug 3873: Avoid software error if the cart contains a deleted record

If a record is placed in the basket and deleted, the basket view
exploded with:
Can't use an undefined value as an ARRAY reference at
/home/koha/src/basket/basket.pl line 73.

Test plan:
1/ Add some records to the basket
2/ Delete one of them
3/ Look at your basket
It should not exploded

Note that the number of items in the basket is now wrong.

Works as expected.
Signed-off-by: Marc Veron <veron@veron.ch>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

basket/basket.pl

@@ -61,6 +61,7 @@ foreach my $biblionumber ( @bibs ) {
     $template->param( biblionumber => $biblionumber );
 
     my $dat              = &GetBiblioData($biblionumber);
+    next unless $dat;
     my $record           = &GetMarcBiblio($biblionumber);
     my $marcnotesarray   = GetMarcNotes( $record, $marcflavour );
     my $marcauthorsarray = GetMarcAuthors( $record, $marcflavour );