An error occurs when using XA transactions：java.lang.NullPointerException

**version:5.3.2**

**Debug:**

After the execution of the init method in XAShardingSphereTransactionManager, the subsequent execution will involve the close method. Inside the close method, the cachedDataSources.clear() operation will be performed.

init, note the object ID @8060

In the close method, the cachedDataSources of the object with ID @8060 is cleared.

When invoking the getConnection method at this point, the cachedDataSources is empty.

Then an error occurs.

The ZookeeperRepository listens for configuration changes and then triggers ShardingSphereTransactionManagerEngine.close.

If I comment out the watch code, the program can run normally without any errors.

**stack trace:**
`Caused by: java.lang.NullPointerException
at org.apache.shardingsphere.transaction.xa.XAShardingSphereTransactionManager.getConnection(XAShardingSphereTransactionManager.java:91)
at org.apache.shardingsphere.transaction.ConnectionTransaction.getConnection(ConnectionTransaction.java:106)
at org.apache.shardingsphere.driver.jdbc.core.connection.ConnectionManager.createConnection(ConnectionManager.java:365)
at org.apache.shardingsphere.driver.jdbc.core.connection.ConnectionManager.createConnections(ConnectionManager.java:334)
at org.apache.shardingsphere.driver.jdbc.core.connection.ConnectionManager.getConnections(ConnectionManager.java:323)
at org.apache.shardingsphere.infra.executor.sql.prepare.driver.DriverExecutionPrepareEngine.group(DriverExecutionPrepareEngine.java:88)
at org.apache.shardingsphere.infra.executor.sql.prepare.AbstractExecutionPrepareEngine.prepare(AbstractExecutionPrepareEngine.java:65)
at org.apache.shardingsphere.driver.jdbc.core.statement.ShardingSpherePreparedStatement.createExecutionGroupContext(ShardingSpherePreparedStatement.java:533)
at org.apache.shardingsphere.driver.jdbc.core.statement.ShardingSpherePreparedStatement.useDriverToExecute(ShardingSpherePreparedStatement.java:508)
at org.apache.shardingsphere.driver.jdbc.core.statement.ShardingSpherePreparedStatement.execute(ShardingSpherePreparedStatement.java:443)`

Start at XAShardingSphereTransactionManager.getConnection and its init and close methods, using the stack trace location at line 91. Then trace how ZookeeperRepository configuration watches trigger ShardingSphereTransactionManagerEngine.close. Done means the XA transaction path no longer raises the reported NullPointerException after a configuration change; the payload does not name a regression test.

Written by the indexing model from the issue text.