Fix a crash in record predicates

Ensures that the argument to a record predicate has enough items to be a
record before checking for the record-marker and type name.

scheme/base.sld

@@ -1973,6 +1973,7 @@
 (define (make-type-predicate pred name)
   (lambda (obj)
     (and (vector? obj)
+         (= (vector-length obj) 3)
          (equal? (vector-ref obj 0) record-marker)
          (equal? (vector-ref obj 1) name))))
 (define (make-constructor make name)