Error handling always throws NotImplemented

[praeclarum]

On this line: https://github.com/mono/debugger-libs/blob/master/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs#L1547

The code always throws NotImplementedException even if there is an error handler.

Should the throw be in an else?

[vargaz]

I think the error handler should not return, but throw some kind of exception.