Remaining org-src.el free variable warnings

[Kyle Meyer <kyle@kyleam.com>]

Compiling org-src.el since 71641bc3a0882b has given free variable
warnings.  One of these was fixed in e50472d926f92c, but some still
remain:

    In org-src--contents-area:
    org-src.el:303:49:Warning: reference to free variable `beg'
    org-src.el:303:53:Warning: reference to free variable `end'

Despite the line numbers given, I think these are referring to the
line marked below (line 284 in org-src.el).

#+begin_src elisp
  (defun org-src--contents-area (datum)
    "Return contents boundaries of DATUM.
  DATUM is an element or object.  Return a list (BEG END CONTENTS)
  where BEG and END are buffer positions and CONTENTS is a string."
    (let ((type (org-element-type datum)))
      (cond
       ((eq type 'footnote-definition)
        (let* ((beg (org-with-wide-buffer
                     (goto-char (org-element-property :post-affiliated datum))
                     (search-forward "]")))
               (end (or (org-element-property :contents-end datum) beg)))
          (list beg end (buffer-substring-no-properties beg end))))
       ((org-element-property :contents-begin datum)
        (list (org-element-property :contents-begin datum)
              (org-element-property :contents-end datum)
              (buffer-substring-no-properties beg end)))  ; <---- HERE
       ((memq type '(example-block export-block src-block))
        [...]
       (t (error "Unsupported element or object: %s" type)))))
#+end_src

Also, what case does that branch of cond cover?

--
Kyle