ox-latex: Utilize change in bcf6970

* ox-koma-letter.el (org-koma-letter-template),
  ox-latex.el (org-latex--format-spec): Tiny refactor.

contrib/lisp/ox-koma-letter.el

@@ -632,7 +632,7 @@ holding export options."
 	       (subject* (org-string-nw-p
 			  (org-export-data
 			   (org-element-parse-secondary-string
-			    (or (plist-get info :subject) "")
+			    (plist-get info :subject)
 			    (org-element-restriction 'keyword))
 			   info)))
 	       (title* (and (plist-get info :with-title)

lisp/ox-latex.el

@@ -1227,17 +1227,17 @@ INFO is a plist used as a communication channel."
 			verbatim))
 	(language (let ((lang (plist-get info :language)))
 		    (or (cdr (assoc lang org-latex-babel-language-alist))
-			lang ""))))
-    `((?a . ,(or (org-export-data (plist-get info :author) info) ""))
-      (?t . ,(or (org-export-data (plist-get info :title)  info) ""))
+			lang))))
+    `((?a . ,(org-export-data (plist-get info :author) info))
+      (?t . ,(org-export-data (plist-get info :title)  info))
       (?k . ,(org-export-data (org-latex--wrap-latex-math-block
 			       (org-element-parse-secondary-string
-				(or (plist-get info :keywords) "") objects)
+				(plist-get info :keywords) objects)
 			       info)
 			      info))
       (?d . ,(org-export-data (org-latex--wrap-latex-math-block
 			       (org-element-parse-secondary-string
-				(or (plist-get info :description) "") objects)
+				(plist-get info :description) objects)
 			       info)
 			      info))
       (?c . ,(plist-get info :creator))