org-export: Fix `org-export-get-category'

* contrib/lisp/org-export.el (org-export-get-category):
  `org-entry-properties' is over-zealous when it comes to "CATEGORY"
  property.  Ignore its "???" return value, which only means it wasn't
  able to find an appropriate category.

diff --git a/contrib/lisp/org-export.el b/contrib/lisp/org-export.el
index 210cdd9..7afcd8d 100644 (file)
--- a/contrib/lisp/org-export.el
+++ b/contrib/lisp/org-export.el
@@ -3268,12 +3268,14 @@ fail, the fall-back value is \"???\"."
                        (org-export-get-parent-headline blob))))
        ;; Almost like `org-export-node-property', but we cannot trust
        ;; `plist-member' as every headline has a `:category'
-       ;; property, even if nil.
+       ;; property, would it be nil or equal to "???" (which has the
+       ;; same meaning).
        (let ((parent headline) value)
          (catch 'found
            (while parent
              (let ((category (org-element-property :category parent)))
-               (and category (throw 'found category)))
+               (and category (not (equal "???" category))
+                    (throw 'found category)))
              (setq parent (org-element-property :parent parent))))))
       (org-element-map
        (plist-get info :parse-tree) 'keyword