空值转换成日期类型报错

目标表有个字段是日期格式的，但源表有些值是空的，转换后老报错。
[INFO] 2021-06-03 17:04:55.815 - [taskAppId=TASK-33-10254-133171]:[127] - -> java.sql.SQLException: TIMESTAMP 类型转换错误：[{"byteSize":0,"rawData":"","type":"STRING"}]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.fillPreparedStatementColumnType(CommonRdbmsWriter.java:497) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.fillPreparedStatement(CommonRdbmsWriter.java:405) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.doOneInsert(CommonRdbmsWriter.java:380) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.doBatchInsert(CommonRdbmsWriter.java:362) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.startWriteWithConnection(CommonRdbmsWriter.java:291) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.startWrite(CommonRdbmsWriter.java:319) [plugin-rdbms-util-0.0.1-SNAPSHOT.jar:na]

Start in plugin-rdbms-util at CommonRdbmsWriter.java, especially fillPreparedStatementColumnType and the surrounding fillPreparedStatement path shown in the stack trace. Reproduce the case with an empty source value mapped to a date or TIMESTAMP column, then verify that the write no longer raises the reported conversion error.

Written by the indexing model from the issue text.