Cryptic message "Error is null"

[jcubic]

Got weird error when writing function that read whole file:

(define (read-file file)
  (call-with-input-file file
    (lambda (port)
      (let loop ((char (read-char port)) (result '()))
        (if (eof-object? char)
            (string (reverse result))
            (loop (read-char port) (cons char result)))))))

The code should call (apply string (reverse result)) but instead of nice error about invalid type I got this error instead:

lips> (read-file "test.txt")
Error is null

[jcubic]

Inside this expression:

(define (read-file file)
  (call-with-input-file file
    (lambda (port)
      (let loop ((char (read-char port)) (result '()))
        (print (string (reverse result)))))))

It only happens if there is read-char if I remove it, I get a normal error:

Expecting character got nil in expression string

[jcubic]

This is simplified reproduction:

(try (begin (Promise.resolve) (typecheck "test" 10 "string")) (finally))

[jcubic]

This gives a NodeJS warning:

(try (try (typecheck "test" 10 "string") (finally)) (catch (e) e))

(node:2390128) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 6)