tie at begin of system with transposing instruments

[Frédéric Bron]

Using lilypond 2.6.4 on Windows (not cygwin)

In the following example, the ties at the beginning of the second system 
are not typeset correctly. It seems that the problem comes from the 
different key of the first instrument: if you remove the "\key af 
\major", everythings looks fine. I had some difficulties to rediuce it 
to such a small example from a big orchestral score because when I 
deleted parts, the bug disappeared!

F. Bron

\version "2.6.4"

\include "english.ly"

\score {
       <<
               \context StaffGroup = AllInstruments <<
                       \context Staff = First <<
                               { \key af \major ef'1 R1*15 }
                       >>
                       \context Staff = Second <<
                               { \repeat unfold 15 { b''2 b''2~ } b''1 }
                       >>
                       \context Staff = Third <<
                               { \repeat unfold 15 { g'2 g'~ } g'1 }
                       >>
               >>
       >>
}