Effect of <> empty chord on spacing

[Mark Knoop]

Not sure if this qualifies as a bug, but it's a little unexpected and
annoying. Using an empty chord to attach markup with full-bar rests
seems to change the spacing of the bars, the bar with the <> is
significantly shorter. Using a zero-duration skip (s1*0) has the same
effect.

This only seems to happen under certain circumstances: when the line is
full, and the rests are ultimately followed by some music.

\version "2.19.18" % same result with "2.18.2"
{
  R1
  <>^\markup \column { attached to <> }
  R1
  R1
  R1^\markup \column { attached to R1 }
  c'1
  \repeat unfold 16 c'16
}

-- 
Mark Knoop