Fix property drawer regexp

* lisp/org.el (org-property-drawer-re): Make sure regexp doesn't expand
  past other drawers.

lisp/org.el

@@ -492,7 +492,7 @@ Group 1 contains drawer's name or \"END\".")
 
 (defconst org-property-drawer-re
   (concat "^[ \t]*:PROPERTIES:[ \t]*\n"
-	  "\\(?:[ \t]*:\\S-+:\\(?: .*\\)?[ \t]*\n\\)*"
+	  "\\(?:[ \t]*:\\S-+:\\(?: .*\\)?[ \t]*\n\\)*?"
 	  "[ \t]*:END:[ \t]*$")
   "Matches an entire property drawer.")