Null value returned from BlobImpl getBytes

If translator retrieveValue return a empty Blob, the engine will throw NPE as below

Caused by: java.lang.NullPointerException
at javax.sql.rowset.serial.SerialBlob.<init>(SerialBlob.java:100)
at org.teiid.common.buffer.LobManager.persistLob(LobManager.java:226)
at org.teiid.common.buffer.LobManager.updateReferences(LobManager.java:141)
at org.teiid.common.buffer.TupleBuffer.addTupleBatch(TupleBuffer.java:203)
at org.teiid.query.processor.BatchCollector.flushBatchDirect(BatchCollector.java:229)
at org.teiid.dqp.internal.process.RequestWorkItem$1.flushBatchDirect(RequestWorkItem.java:653)