bug in gitk: history moves right when scrolling up and down with mouse wheel

Hello,

I don't know yet how to reliably trigger that, but it feels scary.

If that help, it happens with the view

	{karo {} ^linus/master {git for-each-ref --format='%(refname)' refs/remotes/customers/karo refs/heads/karo}}

If I knew how to record a video of my screen, I'd do this. Maybe someone knows? Maybe this report is already enough?

Happens with Debian's git 1:1.7.2.3-2.2.

Best regards Uwe