fix: check for activeElement before calling blur() on it

[DanielRuf]

Description

Replaces #11214

• Closes tests: failing unit tests in IE11 due to blur() being called on null / undefined #11213

Motivation and Context

Fixes the unit tests in IE11 on Windows 10.

Types of changes

• Documentation
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing
  functionality to change)

Checklist (all required):

• I have read and follow the CONTRIBUTING document.
• There are no other pull request similar to this one.
• The pull request title is descriptive.
• The template is fully and correctly filled.
• The pull request targets the right branch (develop or support/*).
• My commits are correctly titled and contain all relevant information.
• My code follows the code style of this project.
• I have updated the documentation accordingly to my changes (if relevant).
• I have added tests to cover my changes (if relevant).
• All new and existing tests passed.

⚠️ Require:

• test: minimize interchange debouce test race condition #11259 test: minimize interchange debouce test race condition

[ncoden]

Tests are subject to race conditions with this PR (as discussed in #11214). Waiting for #11259 to merge.

[DanielRuf]

Mh, we still have the focus / blur issue on IE. Didn't we already fix this? On IE11 is is body.

#11074

[ncoden]

See #11275

[ncoden]

Tests pass with develop merged but there's an issue with BrowserStack. See browserstack/browserstack-runner#201

[DanielRuf]

Hm, even with the change Android 4.4 fails:
https://travis-ci.org/zurb/foundation-sites/jobs/392125882#L1133

[DanielRuf]

I guess their devices are too slow.

[DanielRuf]

Sigh https://travis-ci.org/zurb/foundation-sites/jobs/392135487#L1116

[ncoden]

@DanielRuf I already tried on your branch the changes with this PR #11333 and it works. There's just the browserstack runner bug.

[DanielRuf]

@DanielRuf I already tried on your branch the changes with this PR #11333 and it works. There's just the browserstack runner bug.

What about the linked lines? Firefox and Android 4.4?

[DanielRuf]

Well, then I'll wait and see what happens after the merge or rebase.

[ncoden]

@DanielRuf They still happen time to time. I was only talking about the fails due to timeouts.

[ncoden]

I made some tests and this PR (with a9334ad) introduce the following error:

[Windows 8.1, Firefox 60.0] Error: "closes the targeted submenu" failed, uncaught exception: AssertionError: expected { Object (0, length, ...) } to be hidden (:0)

See https://www.travis-ci.org/ncoden/foundation-sites/jobs/392158100

With a9334ad, tests always fails. The same branch with a9334ad never fails (I ran the tests 5 times)

[DanielRuf]

With a9334ad, tests always fails. The same branch with a9334ad never fails (I ran the tests 5 times)

And IE11 does not fail then if we revert this? Initially we needed this for IE11 and a few other browsers due to the debouncing behavior and race conditions.

Revert it if this resolves the issues.

[ncoden]

Initially we needed this because of:

TypeError: Die Eigenschaft "blur" eines undefinierten oder Nullverweises kann nicht abgerufen werden.

But I never seen this error in our tests. So unless you can reproduce it on browserstack and send me a link I think we can close this PR.

[ncoden]

Racing conditions and tests for debouncing were resolved in others PRs. (#11279)