error parsing b/3079907

[tybug]

from slider import *

library = Library(".")
b = library.lookup_by_id(3079907, download=True, save=True)

b.hit_objects(easy=True)

Traceback (most recent call last):
  File "/Users/tybug/Desktop/Liam/coding/sandbox/_slider.py", line 10, in <module>
    b.hit_objects(easy=True)
  File "/Users/tybug/Desktop/Liam/coding/osu/slider/slider/beatmap.py", line 1967, in hit_objects
    hit_objects = resolve_stacking_method(hit_objects, ar, cs)
  File "/Users/tybug/Desktop/Liam/coding/osu/slider/slider/beatmap.py", line 2073, in _resolve_stacking
    ob_n_end_position = ob_n.curve(1)
  File "/Users/tybug/Desktop/Liam/coding/osu/slider/slider/curve.py", line 198, in __call__
    ts = self._ts
  File "/Users/tybug/Desktop/Liam/coding/osu/slider/slider/utils.py", line 19, in __get__
    value = self._fget(instance)
  File "/Users/tybug/Desktop/Liam/coding/osu/slider/slider/curve.py", line 192, in _ts
    lengths[-1] - (length - self.req_length),
IndexError: list index out of range

only occurs when resolving stacking with easy enabled. Resolving stacking with nomod (easy=False) is fine.