--- trunk/lib/Biblio/Isis.pm	2005/03/12 21:05:29	41
+++ trunk/lib/Biblio/Isis.pm	2006/07/06 11:02:37	44
@@ -475,7 +475,10 @@
 		foreach my $l (@{$row->{$k}}) {
 
 			# filter output
-			$l = $self->{'hash_filter'}->($l) if ($self->{'hash_filter'});
+			if ($self->{'hash_filter'}) {
+				$l = $self->{'hash_filter'}->($l);
+				next unless defined($l);
+			}
 
 			my $val;