[Runtime] Fix not validate IRI items for widget.

According to
http://www.w3.org/TR/widgets/#iri-attribute
http://www.w3.org/TR/widgets/#table-of-elements-and-their-attributes

The id and authorHref are IRI item, and we need validate they,
and if they are illegal they will be empty.

GURL::spec() will return an IRI string but might with a
superfluous '/' at the end, so GURL only used for validate.

Unittest give an invalid ID for parse, and check the result with
the origin string then we will got fail. So set the widget's
(which used to check) ID to empty.