Added error string for NS_ERROR_DOM_RETVAL_UNDEFINED since Nisheeth forgot to do it. R=pollmann.

dom/src/base/domerr.msg

@@ -52,7 +52,7 @@ DOM_MSG_DEF(NS_ERROR_DOM_BAD_DOCUMENT_DOMAIN, "Illegal document.domain value")
 DOM_MSG_DEF(NS_ERROR_DOM_PROP_ACCESS_DENIED, "Access to property denied")
 DOM_MSG_DEF(NS_ERROR_DOM_XPCONNECT_ACCESS_DENIED, "Access to XPConnect service denied")
 DOM_MSG_DEF(NS_ERROR_DOM_BAD_URI, "Access to restricted URI denied")
-
+DOM_MSG_DEF(NS_ERROR_DOM_RETVAL_UNDEFINED, "Return value is undefined")
 
 /* common global codes (from nsError.h) */