Bug Fix: Fix text structure NPE when fields have null value

[weizijun]

when fields have null value, Elasticsearch will return NPE.
I add a check to avoid it.

[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)

[davidkyle]

@weizijun please do you have a stack trace for the NPE?

null values are filtered out here, I can't see a code path where fieldValues could contain a null.

elasticsearch/x-pack/plugin/text-structure/src/main/java/org/elasticsearch/xpack/textstructure/structurefinder/TextStructureUtils.java

Line 332 in b51951f

.filter(fieldValue -> fieldValue != null)

[davidkyle]

Suggested change

	.filter(value -> value != null)
	.filter(Objects::nonNull)

[weizijun]

done

[weizijun]

please do you have a stack trace for the NPE?

Here is a example:
put the file test.json to the kibana upload file page:

{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}
{"field":["a", "b", null]}

it will see the error:

[null_pointer_exception Root causes: null_pointer_exception: null]: null

[davidkyle]

LGTM

Thanks for adding the test case and the example for reproducing the error.

null values are filtered out here, I can't see a code path where fieldValues could contain a null.

I understand now the null check is in the list not the contents of the list and that was causing the problem. Thanks for the fix.

[davidkyle]

@elasticmachine test this please

[davidkyle]

@elasticmachine test this please

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.18
✅	8.19
✅	9.0
✅	8.17