searchAfter with a null date, bring parse_exception

[lisongHo]

Please use the following questions as a guideline to help me answer
your issue/question without further inquiry. Thank you.

Which version of Elastic are you using?

elastic.v7 (for Elasticsearch 7.x)
github.com/olivere/elastic/v7 v7.0.32

Please describe the expected behavior

should not trigging an exception

Please describe the actual behavior

all shard failed
parse_exception
failed to parse date field [-9223372036854776000] with format [strict_date_optional_time||epoch_millis]: [failed to parse date field [-9223372036854776000] with format [strict_date_optional_time||epoch_millis]]

Any steps to reproduce the behavior?

I am using a delivered_at(date) and shipment_id to sort,
For deep pagination , I using searchAfter
but you know , some shipments are not delivered, and the delivered_at would be a null value
then you will return [-9223372036854776000]+shipment_id result.Hits.Hits[len(result.Hits.Hits)-1].Sort

in the next time , I using [-9223372036854776000]+shipment_id as a cursor to search next page, es will return a parse_exception

In Java, using Long.MIN_VALUE[-9223372036854775808] to represent a null Date

so I try to change [-9223372036854776000] to [-9223372036854775808], it worked !

Although we can solve this problem by modifying our own code, but I still hope you can help solve the problem from the root when you have free time

Your project has been of great help to us
thank you very much~