the abcd scrollbar disapear too early

[cm-t 🦄🏂🌈🎵]

0. When looking for a contact,
1. I scroll
2. that ABCD scrollbar appears, it is cool, you want to find that first letter of your contact
3. Let's says it is [M]um
4. my brain understand I want 'M'
5. I find it on the scrollbar
6. I put my finger on 'M'
7. tap it
8. but during those milliseconds (4.5.6) the abcd scroll bar has disappear, means my click will happen on a contact, not the ABCD scrollbar.
(that behaviour will create new unwanted step, back to contact list, scroll to make re-appear the scroll bar and eventually click on it with success, or just forfeit and manually scroll to the contact)

(I've seen that bug for month/years, not a new regression)