Rendering to *output-stream* gives different result than rendering to string

[kisp]

Hi,

while playing around with rendering to *output-stream* versus rendering to a string, I got the following:

CL-USER> (use-package :cl-markup)
T
CL-USER> (markup (:ul (loop for item in '(1 2 3) collect (markup (:li item)))))
"<ul><li>1</li><li>2</li><li>3</li></ul>"
CL-USER> (let ((*output-stream* t))
           (markup (:ul (loop for item in '(1 2 3) collect (markup (:li item))))))
<ul><li>1</li><li>2</li><li>3</li></li></li></li></ul>
"</ul>"
CL-USER> 

Note the additional and unexpected closing tags </li> in the second output.

Is this invalid client code or a bug?

If it is a bug, perhaps the expansion under the (IF *OUTPUT-STREAM* regime should generate a PROGN that contains NIL as its last form.

In the above example, the last form of the PROGN is (WRITE-STRING "</li>" *OUTPUT-STREAM*).

[kisp]

That fixes it for me https://github.com/kisp/cl-markup/commit/703a6a4087ee4de948b83f61874024de29e2a004

Should I open a pull request?