MIDI dynamic bug

[Gilberto Agostinho]

Dear bug squad,

Today I found a bug related to MIDI playback. If I use set the 
TimeSignature's stencil to false in the following way below, the first 
dynamic is ignored. Commenting out that override produces the correct 
result. This affects only the very first note of the playback, all 
others are played normally.

\version "2.19.28"

A = {
  \override Score.TimeSignature.stencil = ##f
  c'4  d' e' f'
}

B = {
  s4\ppppp s\f s\ppppp s\f
}

\score {
  \new Staff << \A \B>>
  \midi{}
  \layout{}
}

Let me know if I can be of any help to further investigate this bug.

Cheers,
Gilberto