Axis_group_interface::part_of_line_pure_height (Grob *me, bool begin, int start, int end)
{
Spanner *sp = dynamic_cast<Spanner *> (me);
+ if (!sp)
+ return Interval (0, 0);
SCM cache_symbol = begin
? ly_symbol2scm ("begin-of-line-pure-height")
: ly_symbol2scm ("rest-of-line-pure-height");