Fix ContainerHelper for .container retrieval (#200)

This commit is aware of the difference between _container and container_ in old versions of SerializedFile.py for compatibility.

Author: t-wy

UnityPy/files/ObjectReader.py

@@ -139,11 +139,7 @@ def set_raw_data(self, data):
 
     @property
     def container(self):
-        return (
-            self.assets_file._container[self.path_id]
-            if self.path_id in self.assets_file._container
-            else None
-        )
+        return self.assets_file._container.path_dict.get(self.path_id)
 
     @property
     def Position(self):

UnityPy/files/SerializedFile.py

@@ -653,7 +653,7 @@ def __init__(self, container) -> None:
         self.container = container
         # support for getitem
         self.container_dict = {key: value.asset for key, value in container}
-        self.path_dict = {value.asset.path_id: value.asset for key, value in container}
+        self.path_dict = {value.asset.path_id: key for key, value in container}
 
     def items(self):
         return ((key, value.asset) for key, value in self.container)