close-update deadlock

[AshleyYakeley]

This deadlocks:

#!/usr/bin/env -S pinafore
import "pinafore-gnome" in
with GTK. in
run.GTK $ fn gtk =>
let

    eui: Element
    = exec.Element $ do
        sleep $ Seconds 0.2;
        pure.Action blank.Element;
        end;

in do
    ref <- newMem.WholeModel;
    w <- open.Window gtk (600,800) {"Window"} $ dynamic.Element $ coMap.WholeModel (fn _ => eui) ref;
    ref := ();
    sleep $ Seconds 0.1;
    close.Window w;
    end

[AshleyYakeley]

Fixed.