Closing modal with ESC is interrupted by datepicker

[peterblazejewicz]

Bug description:

If there is a datepicker component with an overlay, which uses ESC key within parent modal, also with ESC key feature enabled, opening the datepicker and then closing it with ESC, disabled effectively the ESC feature on the container modal, requiring user to perform additional action to refocus any content within modal.

This is probably related to: #3317

This could be repeated with default demo content:

https://stackblitz.com/run?file=app/modal-basic.ts
https://ng-bootstrap.github.io/#/components/modal/examples#basic

• open basic demo modal, it comes with the datepicker component
• use keyboard to focus the datepicker button
• open datepicker but do not pick a date
• instead close the picker using the ESC key (works)
• now you should be back to modal container
• being in the modal, try to use ESC key again

Link to minimally-working StackBlitz that reproduces the issue:

As stated, this is repeatable with demo content:
https://ng-bootstrap.github.io/#/components/modal/examples#basic

Versions of Angular, ng-bootstrap and Bootstrap:

Angular: n/a

ng-bootstrap:
5.1.1

Bootstrap:
n/a