ambitus engraver and transposed clef

[Nancho Alvarez]

> I'm not top posting.

% This bug is not important, it happens when:
% 1. use the ambitus engraver
% 2. a clef transposed one octava down
% 3. the first note is above the staff

% Lilypond compiles it perfectly but it says:
% programming error: Adding reverse rod
% continuing, cross fingers


\version "2.11.22"

{ \clef "G_8" g' }

\layout{
        \context{\Staff \consists Ambitus_engraver }
}