Do not pass in undefined onOutsideClick to the OutsideClickHandler

[majapw]

Fixes #1227

So I know we have #1239 open, but as an alternative, I wanted to propose this option instead as it wouldn't add the document event listeners at all (which seems preferable?).

As for regression tests, @ljharb, we render withPortal datepickers in tests, shouldn't the proptype error show up there?

to: @ljharb

[majapw]

@ljharb in fact, they do show up, but as warnings and not as errors? Is there any way to change that?

[coveralls]

Coverage increased (+0.02%) to 84.453% when pulling 095864c on maja-address-on-outside-click-errors into 5f55b62 on master.

[ljharb]

it seems like we should be able to avoid adding the wrapping div entirely by only rendering the wrapper when enableOutsideClick is true?

[majapw]

I was thinking that I didn't want to change the DOM structure in this PR, but this is true. Do you think it could potentially cause problems if we removed this div?

[ljharb]

Hmm, I can't see why

[majapw]

@ljharb would you like to take another look?

[ljharb]

it seems like we could avoid the array, and the keys, if we did:

{enableOutsideClick && (
  <OutsideClickHandler…
)}
{!enableOutsideClick && input}
{!enableOutsideClick && this.maybeRenderDayPickerWithPortal()}

[majapw]

i was thinking about that but wasn't sure if that was preferable.

I guess making an array every time is p. gross. I'll update it