my %opt = @_;
my $field = delete($opt{field}) || 'taxproductnum';
my $pkgpart = delete($opt{pkgpart});
-my $part_pkg = FS::part_pkg->by_key($pkgpart);
-my %pkg_options = $part_pkg->options;
-$pkg_options{'usage_taxproductnum_'} = $part_pkg->taxproductnum;
+my %pkg_options;
+if ($pkgpart) {
+ my $part_pkg = FS::part_pkg->by_key($pkgpart);
+ my %pkg_options = $part_pkg->options;
+ $pkg_options{'usage_taxproductnum_'} = $part_pkg->taxproductnum;
+}
my @classes = qsearch('usage_class', { 'disabled' => '' });
unshift @classes,