collision at end of system with clef and change staff

[Wilbert Berendsen]

> I'm not top posting.

%{
A clef at the end of a line gets overwritten by music when the music
switches away from that staff after the clef change.
When the change is in the middle of a line, the clef does not collide.

The first score shows the collision.
The second score is the same as the first, except without the break to
show that in the middle of a line the clef does not collide.
%}

\version "2.11.28"
\paper { ragged-right = ##t }
\new PianoStaff <<
        \new Staff = "rh" \relative c' { \time 3/8
                c16 d e
                \change Staff = lh
                e d c
                \clef bass
                \break  % force a new line
                \change Staff = rh
                c d e f g a
        }
        \new Staff = "lh" {s4. s4.}
>>
\new PianoStaff <<
        \new Staff = "rh" \relative c' { \time 3/8
                c16 d e
                \change Staff = lh
                e d c
                \clef bass
                \change Staff = rh
                c d e f g a
        }
        \new Staff = "lh" {s4. s4.}
>>