Tooltip not closing automatically on scroll

[dimpuprasad]

Bug description:
Tooltip has been added inside a scrollable container, after hovering on tooltip and then scrolling within the container doesnt automatically close the tooltip.

To reproduce the issue:

1. Hover on a button
2. as soon as the hovered text is displayed, scroll down within the container, without moving mouse pointer anywhere.

Issue:
The hovered text also moves on scroll, and once the mouse pointer is moved a bit, then it closes.

StackBlitz: https://stackblitz.com/edit/angular-ngxbootstrap-tooltip-twjhhcns?file=src%2Fapp%2Fapp.component.html

Versions of ngx-bootstrap, Angular, and Bootstrap:

ngx-bootstrap: 3.3.0

Angular: 5.2.0

Expected behavior

Displayed text on hover must automatically close on scroll.