p-dropdown onChange - return null when using keyboard navigation

[AvshT]

When using the keyboard navigation in the dropdown dialog, the onChange emits on every Up/Down navigation.
The $event object values are:
{originalEvent, value}
The originalEvent returns null, it's supposed to have the keyboard event object.

@yigitfindikli Link to the specific line:
94e7c5b#r61496329

Thank you for your support.

[yigitfindikli]

5d2ec15