improved error logging and handling

app/lib/features/web_feed/utils/feed_parser.dart

@@ -92,7 +92,7 @@ class FeedParser {
           tags: tags,
         );
       default:
-        throw Exception();
+        throw Exception('Unknown feed type in readGeneralData: ${_feed.runtimeType}');
     }
   }
 
@@ -209,7 +209,7 @@ class FeedParser {
           );
         }).toList();
       default:
-        throw Exception();
+        throw Exception('Unknown feed type in readArticles: ${_feed.runtimeType}');
     }
   }
 }