Apparently bogus warning with 2.15.12

[Nick Payne]

I'm setting Bach's BWV853 (Prelude from WTC 1), using showLastLength to 
just engrave the last six bars added, and as I add bars I'm getting  
warnings about unterminated ties that come and go as the bars are added. 
The reason I say the warning is bogus is because there are no ties 
across barlines anywhere in the piece, and when I have a look at the 
bar(s) being complained of, there are no ties anywhere near. I spent 
about half an hour trying to get a small test case to reproduce the 
problem, but was not successful. I don't recall getting this warning 
with previous versions of Lilypond except when there really was a tie 
across the bar where the engraving started. Console log sample below.

Processing `C:/Users/Nick/Documents/lilypond/bwv853a.ly'
Parsing...
Interpreting music...
C:/Users/Nick/Documents/lilypond/bwv853a.ly:94:13: warning: unterminated tie
<g e
             cs>\arpeggio r4 r16 fs e d \offset "Slur" #'(0 . 0.3) 
cs\arpeggio( d)

C:/Users/Nick/Documents/lilypond/bwv853a.ly:94:11: warning: unterminated tie
<g
           e cs>\arpeggio r4 r16 fs e d \offset "Slur" #'(0 . 0.3) 
cs\arpeggio( d)

C:/Users/Nick/Documents/lilypond/bwv853a.ly:94:9: warning: unterminated tie
<
         g e cs>\arpeggio r4 r16 fs e d \offset "Slur" #'(0 . 0.3) 
cs\arpeggio( d)

Preprocessing graphical objects...


Nick Payne