This very specific combination of circumstances causes Lily to core dump:
1. A length-1 tuplet (ie, tuplet containing only a single note or rest);
2. occurs as the last element of a measure; followed by
3. more music in the following measure; and with
4. proportional spacing turned on and set to a value that is "too tight"
GNU LilyPond 2.19.82
Preprocessing graphical objects...
Finding the ideal number of pages...
Fitting music on 1 page...
failed assertion `!is_empty ()'
Increasing proportional spacing from 1/16 up to, say, 1/32 makes the
problem go away; this is the workaround to document until the bug is fixed.
(Choice of time signature, multiplier of the tuplet, vertical position of
notes on the staff all make no difference in resulting behavior.)
I think the problem's been in Lily for a while (it's definitely not a
2.19.82-only bug); it entered sometime during or after 2014.