Fix export of empty items in HTML and DocBook

lisp/org-docbook.el

@@ -1378,7 +1378,7 @@ the alist of previous items."
     (cond
      ;; At an item: insert appropriate tags in export buffer.
      ((assq pos struct)
-      (string-match (concat "[ \t]*\\(\\S-+[ \t]+\\)"
+      (string-match (concat "[ \t]*\\(\\S-+[ \t]*\\)"
 			    "\\(?:\\[@\\(?:start:\\)?\\([0-9]+\\|[a-zA-Z]\\)\\]\\)?"
 			    "\\(?:\\(\\[[ X-]\\]\\)[ \t]+\\)?"
 			    "\\(?:\\(.*\\)[ \t]+::[ \t]+\\)?"

lisp/org-html.el

@@ -2482,7 +2482,7 @@ the alist of previous items."
      ;; At an item: insert appropriate tags in export buffer.
      ((assq pos struct)
       (string-match
-       (concat "[ \t]*\\(\\S-+[ \t]+\\)"
+       (concat "[ \t]*\\(\\S-+[ \t]*\\)"
 	       "\\(?:\\[@\\(?:start:\\)?\\([0-9]+\\|[A-Za-z]\\)\\]\\)?"
 	       "\\(?:\\(\\[[ X-]\\]\\)[ \t]+\\)?"
 	       "\\(?:\\(.*\\)[ \t]+::[ \t]+\\)?"