Update CassetteBlock attributes to correct types

Change attributes in CassetteBlock class to use appropriate types.

Author: TsunaMoo

games/game_cassettebeasts.py

@@ -65,8 +65,8 @@ def fix(self, filetree: mobase.IFileTree) -> mobase.IFileTree:
 
 class CassetteBlock:
     def __init__(self):
-        compressed_size: str = "(unknown)"
-        data: str = "(unknown)"
+        self.compressed_size: int = 0
+        self.data: bytes = b''
 
 class CassetteBeastsSaveGame(BasicGameSaveGame):
     def __init__(self, filepath: Path):