fix duplicate GlobalObjectIdHash & not save problem

[slb1988]

Duplicate GlobalObjectIdHash come out always, globalObjectId got null in some phase like PrefabImporterEditor::OnDestroy, another problem is GlobalObjectIdHash changed but prefab don't.

Changelog

• Added: The package whose Changelog should be added to should be in the header. Delete the changelog section entirely if it's not needed.
• Fixed: If you update multiple packages, create a new section with a new header for the other package.
• Removed/Deprecated/Changed: Each bullet should be prefixed with Added, Fixed, Removed, Deprecated, or Changed to indicate where the entry should go.

Testing and Documentation

• No tests have been added.
• Includes unit tests.
• Includes integration tests.
• No documentation changes or additions were necessary.
• Includes documentation for previously-undocumented public API entry points.
• Includes edits to existing public API documentation.