Controls vis - safely handle case where value can not be extracted from Kibana filter

[nreese]

fixes #22607

The original error can be created with the following steps:

1. Create a new Controls visualization with an Options list control. Set index-pattern and field.
2. Interact with the options list control and select a value and click Apply changes so a filter pill is added to Kibana.
3. Change the field for the options list control. When the new field is applied then the error will be shown.

This resulted in passing [{value: undefined, label: undefined}] to EuiComboBox for the selectedOptions props.

This regression was introduced by PR #20002

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[chrisdavies]

LTGM w/ the tweaks I mentioned.

I pulled it down and tested in both master and this branch. Master reproduced the error, this branch did not. 🎉 🎂

[chrisdavies]

The entire filter could become this: .filter(value => value != null), if you want to keep the != instead of !==. Alternatively, it could be: .filter(value => typeof value !== 'undefined' && value !== null).

[chrisdavies]

This if is unnecessary, as the filter will mean that reduce will be operating over an empty array in the test case, which should be just fie.

[nreese]

If the filter removes all items from the array then reduce would return []. The function should return undefined if there are no selected options.

[chrisdavies]

Just double-checking that you wanted a == instead of a ===. Might want to slap a comment in here, if you do, as this is usually frowned upon, but it is a handy way to check for null and undefined simultaneously.

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[Shifter2600]

Great can't wait to use the new version and test this out in my system that errors currently. I use Docker Kibana 6.4 currently and can pull a new version when this is ready.