Combobox with virtualization not showing last entry when using scrollbar down arrow

[JasonGemDat]

Describe the bug

Last entry of the combobox component does not show up when virtualisation with pagesize property is enabled. If you use your mouse to scroll down the combobox works as expected, but by just clicking the down arrow of the scrollbar and you reach to the end of the combobox, the last entry will be empty.

To Reproduce

Steps to reproduce the behavior:

1. Go to https://stackblitz.com/edit/angular-9l33ci?file=src/app/app.component.ts
2. Open the combobox
3. Spam the click down arrow button from the scrollbar until you reach the end (do not hold the left mouse button)

Expected behavior

The last entry of the combobox will be shown.

Screenshots

Down arrow from scrollbar:

Example of wrong combobox: