check close condition on poll

crsn_screen/src/exec.rs

@@ -107,6 +107,11 @@ impl OpTrait for ScreenOp {
                 let backend: &mut Backend = state.ext_mut();
                 match &mut backend.window {
                     Some(w) => {
+                        if !w.is_open() {
+                            // TODO...
+                            std::process::exit(0);
+                        }
+
                         w.update();
                     }
                     None => {