Help? How to delete automatically-generated notes?

While correcting a few errant commits, I have ended up with a homeless note (and a corresponding pointer “[1 note]” in my graph) which was automatically generated:


the note in the commit looks like this:


but the commit #6ed7411c no longer exists (it was force-pushed out of existence).

How can I delete this note, which no longer serves any purpose?

Thanks in advance,