使用nutzdao和druid结合做数据操作时最近遇到一个怪问题，代码片段如下

        Trans.begin();
        Connection conn = Trans.getConnectionAuto(dao.getDataSource());
        CallableStatement cs = conn.prepareCall("?=call function(?,?)", ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
        cs.registerOutParameter(1, java.sql.Types.INTEGER);
        for (int i = 0; i < params.length; i++)
            cs.setObject(i + 2, params[i]);
        cs.execute();

偶尔会出现 java.lang.ArrayIndexOutOfBoundsException: null 这个异常 ，堆栈如下

java.lang.ArrayIndexOutOfBoundsException: null
	at java.util.ArrayList.add(ArrayList.java:474) ~[?:1.8.0]
	at com.alibaba.druid.pool.DruidPooledConnection.transactionRecord(DruidPooledConnection.java:730) ~[druid-1.1.20.jar:1.1.20]
	at com.alibaba.druid.pool.DruidPooledStatement.transactionRecord(DruidPooledStatement.java:285) ~[druid-1.1.20.jar:1.1.20]
	at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:491) ~[druid-1.1.20.jar:1.1.20]

能是哪的问题呢， 现象还不能重现。