BC in extractArgument() function

[diwms]

Hi there 👋

I've upgraded elasticsearch/elasticsearch library from version 6.1.0 to 6.8.0 and observed interesting situation after some investigations I come to conclusion that this change is BC break. See the screenshot:

Basically, because of extra casting $value variable to an array, in case if body is an object - keys are corrupted.

I'm working on a fix in the own codebase, but meanwhile, maybe there is something behind this change? Maybe some configurations or etc.
If this will be confirmed as a bug I can also work on a PR with proper reproducing test case and fix.

Thanks!