[bug] Exporting results in "Wrong type argument" when "+CALL" is used

[Rodrigo Morales <moralesrodrigo1100@gmail.com>]

As the subject states, executing some exporting commands (see list in
step 2 below) results in an error when there is at least one "#+CALL"
statement.

The backtrace is shown below.

#+begin_example
Debugger entered--Lisp error: (wrong-type-argument consp nil)
  org-babel-exp-code(nil lob)
  org-babel-exp-do-export(nil lob)
  org-babel-exp-process-buffer()
  org-export-as(md nil nil nil nil)
  org-export-to-buffer(md "*Org MD Export*" nil nil nil nil nil #f(compiled-function () #<bytecode 0x156896a2a639>))
  org-md-export-as-markdown(nil nil nil)
  (lambda (a s v b) (org-md-export-as-markdown a s v))(nil nil nil nil)
  org-export-dispatch(nil)
  funcall-interactively(org-export-dispatch nil)
  call-interactively(org-export-dispatch nil nil)
  command-execute(org-export-dispatch)
#+end_example

You can reproduce this bug by

1. Open the file =main.org= by loading the =init.el= file (see
   attachments). You can accomplish this by executing the following
   command.

#+begin_src sh
emacs -Q -l ~/Downloads/init.el ~/Downloads/main.org
#+end_src

2. Execute any of the following
  + =org-md-export-to-markdown=.
  + =org-latex-export-as-latex=.
  + =org-html-export-as-html=.

3. The error might occur.

I'm currently using GNU Emacs 27.1

-- 
Greetings,
Rodrigo Morales.