NullPointerException issue for unsupported database

I’m using liquibase with ctreeACE which is not supported by liquibase. Since current stable version 2.0.5 has an NPE issue (see NPE with UnsupportedDatabase ) for unsupported database, I grabbed the 3.0.0Snapshot source code. But unfortunately I have encountered another NPE issue:
JdbcDatabaseSnapshotGenerator::readColumn(Map<String, Object> columnMetadataResultSet, Relation table, Database database):

                try {
                    if (columnSelectRS.getMetaData().isAutoIncrement(1)) {
                    } else {
                } finally {
                    try {
                    } catch (SQLException ignore) {
                    columnSelectRS.close();                        /////Here NPE thrown

According to JDBC 4 API specifications, closing a Statement object will close and invalidate any instances of ResultSet
produced by that Statement object.  So it is recommended the line columnSelectRS.close() be moved before the line statement.close().

The issue only occurs when the two tables databasechangelog and databasechangeloglock exist according my simple test.