Add assertion for copy-on-failure? type.

Closes #987.

lib/srfi/231/test.sld

@@ -3787,6 +3787,7 @@
                 (vector 'foo 'bar 'baz))
                (make-interval '#(1)))
               (make-interval '#()))))
+        (test-error (specialized-array-reshape A-ref (make-interval '#(100)) 'a))
         )
 
       (test-group "curry tests"

lib/srfi/231/transforms.scm

@@ -579,6 +579,7 @@
                (= (interval-volume (array-domain array))
                   (interval-volume new-domain))))
   (let ((copy-on-failure? (and (pair? o) (car o))))
+    (assert (boolean? copy-on-failure?))
     (cond
      ((reshape-without-copy array new-domain))
      (copy-on-failure?