Scroll "stuck" after selecting the last element, multiple times

[mirela999]

Great directive, thanks! I have an issue in the current provided example: https://stackblitz.com/edit/ng-mat-select-infinite-scroll Reproduction:

1. Open the "select" and select "Option 4".
2. Close the "select", reopen and select "Option 6"
3. Close the "select", reopen and select "Option 8"
4. Close the "select", reopen it, Now the scroll bar doesn't move down - it's like we are at the end of the list, but it's not correct.