Github user yanghua commented on the issue:
https://github.com/apache/flink/pull/6231
@zentol we really caused this exception, in our inner Flink version, we
customized flink-table and implemented stream and dim table join. I think the
default constructor is needed by deserialization.
Whatever it takes, the author who wrote this code misunderstood the
variable `nestedSerializers ` could be null(in current case), but it did not
happens. The truth is : the elements in `nestedSerializers` could be null.
We add a judgement and fixed this NPE, now it works OK.
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