Using index-unsafe on an empty vector errors with should be a non-negative integer below 0 (SBCL)

[Izaakwltn]

Minute and insignificant issue, but it might be worth handling this error from Coalton with a clearer (and potentially attainable) error message:

(in-package #:coalton-user)

(coalton-toplevel

  (define empty-vector
    (vector:make))

  (define (index-empty-vector)
    (vector:index-unsafe 0 empty-vector)))

Returns the error:

Invalid index 0 for (COMMON-LISP:VECTOR COMMON-LISP:T 0), should be a non-negative integer below 0.
   [Condition of type SB-INT:INVALID-ARRAY-INDEX-ERROR]