This is the secondary cause of https://github.com/ppy/osu/issues/28577,
because you could do the following:
- Have a break autogenerate itself
- Adjust either end of it to make it mark itself as manually-adjusted
- Remove all objects before or after said break
to end up in a state wherein there are no objects before or after a
break.
The direct fix is still correct because it is still technically possible
to end up in a state wherein a break is before or after all objects
(obvious one is manual `.osu` editing), but this behaviour is also
undesirable for the autogeneration logic.
