Eff 3.0 hangs on handlers which handle invalid operations

[andrejbauer]

If in pervasives.eff we do this (notice r#print _ k):

let state r x = handler
  | val y -> (fun _ -> y)
  | r#print _ k -> (fun s -> k s s)
  | r#update s' k -> (fun _ -> k () s')
  | finally f -> f x;;

then eff 3.0 hangs.

[matijapretnar]

Closed because this bug doesn't occur in the development branch.