ox: Small refactoring

* lisp/ox.el (org-export-output-file-name): Small refactoring.

lisp/ox.el

@@ -5983,21 +5983,15 @@ Return file name as a string."
 	  ;; property, assuming point is at beginning of said
 	  ;; sub-tree.
 	  (file-name-sans-extension
-	   (or (and subtreep
-		    (org-entry-get
-		     (save-excursion
-		       (ignore-errors (org-back-to-heading) (point)))
-		     "EXPORT_FILE_NAME" 'selective))
+	   (or (and subtreep (org-entry-get nil "EXPORT_FILE_NAME" 'selective))
 	       ;; File name may be extracted from buffer's associated
 	       ;; file, if any.
 	       (and visited-file (file-name-nondirectory visited-file))
 	       ;; Can't determine file name on our own: Ask user.
-	       (let ((read-file-name-function
-		      (and org-completion-use-ido 'ido-read-file-name)))
-		 (read-file-name
-		  "Output file: " pub-dir nil nil nil
-		  (lambda (name)
-		    (string= (file-name-extension name t) extension)))))))
+	       (read-file-name
+		"Output file: " pub-dir nil nil nil
+		(lambda (name)
+		  (string= (file-name-extension name t) extension))))))
 	 (output-file
 	  ;; Build file name.  Enforce EXTENSION over whatever user
 	  ;; may have come up with.  PUB-DIR, if defined, always has
@@ -6011,7 +6005,7 @@ Return file name as a string."
 	   (t (concat (file-name-as-directory ".") base-name extension)))))
     ;; If writing to OUTPUT-FILE would overwrite original file, append
     ;; EXTENSION another time to final name.
-    (if (and visited-file (org-file-equal-p visited-file output-file))
+    (if (and visited-file (file-equal-p visited-file output-file))
 	(concat output-file extension)
       output-file)))