HubExtensions.PushAndLockScope can destroy the DisableHub instance

[jamescrosswell]

Bit of an edge case but I just bumped into this:

sentry-dotnet/src/Sentry/HubExtensions.cs

Line 168 in 34d8490

public static IDisposable PushAndLockScope(this IHub hub) => new LockedScope(hub);

LockedScope is defined as:

sentry-dotnet/src/Sentry/HubExtensions.cs

Lines 186 to 197 in 34d8490

	private sealed class LockedScope : IDisposable
	{
	private readonly IDisposable _scope;
	public LockedScope(IHub hub)
	{
	_scope = hub.PushScope();
	hub.LockScope();
	}
	public void Dispose() => _scope.Dispose();
	}

In GlobalMode, hub.PushScope() returns DisabledHub.Instance:

sentry-dotnet/src/Sentry/Internal/SentryScopeManager.cs

Lines 49 to 55 in 941d9dc

	public IDisposable PushScope<TState>(TState? state)
	{
	if (IsGlobalMode)
	{
	_options.LogWarning("Push scope called in global mode, returning.");
	return DisabledHub.Instance;
	}

Ao if someone did something like:

private void OnButtonClick(EventArgs args)
{
    using lockedHub = hub.PushAndLoclScope();
    // Do some work
}

...in GlobalMode, the instance of DisabledHub would be disposed of when this event handler completed.

I'm assuming we would never want that to happen. We could prevent this by returning some kind of FakeDisposable from HubExtensions.PushAndLockScope if GlobalMode was enabled.