AutoCompleteBox - Internal TextBox is NULL in case of getting focus (Intermittent)

[karena88]

Need to add defensive coding in OnGotFocus method of AutoCompleteBox.
All other usages are under safety check except this one. Time to time it is remaining null if focus is controlled externally.

AutoCompleteBox.cs >>>
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
FocusChanged(HasFocus());
TextBox.Focus(); // Should be if (TextBox != null) TextBox.Focus()
}