Device: Blank flags on v1 WVDs when migrating

This flag was technically used before this project and to ensure it will be unused and ready for safe use in this project and on v3 (if/when), we should blank the flags.

pywidevine/device.py

@@ -6,7 +6,7 @@ from enum import Enum
 from pathlib import Path
 from typing import Any, Optional, Union
 
-from construct import BitStruct, Bytes, Const, ConstructError
+from construct import BitStruct, Bytes, Const, ConstructError, Container
 from construct import Enum as CEnum
 from construct import Int8ub, Int16ub
 from construct import Optional as COptional
@@ -184,6 +184,7 @@ class Device:
         if header.version == 1:  # v1 to v2
             data = _Structures.v1.parse(data)
             data.version = 2  # update version to 2 to allow loading
+            data.flags = Container()  # blank flags that may have been used in v1
 
             vmp = FileHashes()
             if data.vmp: