Error message when rotate has the wrong number of arguments is uninformative

[markromanmiller]

Error in `cross()`:
! `cross` expects both arguments to inherit from `dddr_vector3`. Instead, the arguments were `NULL` and `NULL`.
Backtrace:
 1. dddr::rotate(...)
 2. dddr:::rotate.dddr_quat(...)
 3. dddr:::make_rotator(axis, angle, from, to)
 4. dddr::cross(from, to)