feed->type is require on feedapi_feed_object but not consistently set

in module parser_common_syndication, function parser_simplepie_feedapi_feed, operation 'compatible', when the feed is cached, the type of the feed is not persisted to the cache. Therefore on line 37, on subsequent calls (re: nodeapi/update) the type is not subsequently retrieved (it's null).

This patch persists the type to the cache so it is later retrieved correctly.