Every NSObject allocates native memory for `NSObjectData` via a `NSObjectDataHandle` critical handle. When the handle dies, the memory wasn't reclaimed because `IsInvalid` method was implemented incorrectly. Fixing this bug, leads to crashes in `ReleaseManagedRef` which tries to access the native data that was already freed. Normally, this shouldn't happen because `NSObject` is a normal finalizable object and `NSObjectDataHandle` is a critical finalizable object. This means that the finalizer for `NSObject` would always run first, considering that the 2 objects die at the same time. This means that the native `NSObjectData` would be cleared only after the finalizer for `NSObject` has run and `ReleaseManagedRef` finished executing. However, this is not the case because the "finalization" code of `NSObject` is not run from the finalizer thread but it is enqueued to `NSObject_Disposer`. This means that now the critical finalizer could have actually released the native memory before the finalization of the `NSObject` is done.The simple fix for this is to create a GCHandle keeping the `NSObjectDataHandle` alive until all `NSObject` finalization is done, at the end of `ReleaseManagedRef`.