make sure reference_fields/reference_columns is not undef

diff --git a/lib/SQL/Translator/Parser/DDL/MySQL.pm b/lib/SQL/Translator/Parser/DDL/MySQL.pm
index 1ec752a..b7e05a0 100644 (file)
--- a/lib/SQL/Translator/Parser/DDL/MySQL.pm
+++ b/lib/SQL/Translator/Parser/DDL/MySQL.pm
@@ -136,7 +136,7 @@ role SQL::Translator::Parser::DDL::MySQL {
                     $constraint = ForeignKey->new({ name => $cdata->{name} || '',
                                                     table => $table,
                                                     reference_table => $cdata->{reference_table},
-                                                    reference_columns => $cdata->{reference_fields},
+                                                    defined $cdata->{reference_fields} ? (reference_columns => $cdata->{reference_fields}) : (),
                                                     on_delete => $cdata->{on_delete} || $cdata->{on_delete_do},
                                                     on_update => $cdata->{on_update} || $cdata->{on_update_do} });
                     $table->get_column($_)->is_foreign_key(1) for @{$cdata->{fields}};