When a user opens the calendar popup and a date hasn't been selected and then click the back button on the browser window, the calendar popup doesn't close and stuck on the top left corner without any opportunity to close.
Steps to reproduce:
1. click on 'go to calendar' link.
2. open calendar popup using focus on date input.
3. click back button on the browser window (main window, not a stackblitz frame)
Result in attaches.
https://stackblitz.com/edit/angular-33rslp