Avalonia: Convention based binding throws exception for MenuItem controls

[armstrom]

When relying on convention based bindings for menu items an exception is thrown: "System.Exception: 'No target found for method FileExit.'".

The issue only occurs if a matching method name is found in the ViewModel, if no method with a matching name is present then there is no exception. This indicates that Caliburn is attempting to wire up the command but failing to properly do so. If explicit binding is made to the same handler in the view model, everything works as expected. This issue does not seem to impact other action source types that I've tested such as Buttons which bind by convention properly.