Make representative_card() return only dict

 draft = {"app": ["p-name", "u-url", "u-logo", "u-photo"]}
 
 
-def representative_card(mf2json: dict, source_url: str):
+def representative_card(mf2json: dict, source_url: str) -> dict:
     """
     Return the representative card for given parsed document.
 

         return match
     if match := _check_url_matches_source_url(cards, source):
         return match
+    return {}
 
 
 def _check_uid_and_url_match_source_url(cards, source_url):  # FIXME same as below?