The following minimal example generates the error "programming error:
cannot align on self: empty element" in the console log.
\version "2.13.58"
\relative c' {
\tempo 4 = 72
\override Score.MetronomeMark #'stencil = ##f
c4 c c c
}
Comment out either the \tempo indication or the override and the error
goes away. I use this combination of commands in the \score block quite
often if I want the midi output to play at a particular speed for
proofing, but I don't want a tempo indication to appear in the score.
Having the error appear in the log doesn't seem to affect either the midi
output or the printed score.
Nick