Close #876 - fix todo modal editing feeling slow

Fixes #876. The modal shown when editing todos was feeling slow to start
It required an additional hit of `Enter` to show the modal.

This commit fixes it by queueing a `Draw` update - so now the modal
feels fast to show.

Tests:
* ran `make test`
* tested locally with a todo list

modules/todo/widget.go

@@ -181,6 +181,10 @@ func (widget *Widget) updateSelected() {
 
 	widget.addButtons(form, saveFctn)
 	widget.modalFocus(form)
+
+	widget.app.QueueUpdate(func() {
+		widget.app.Draw()
+	})
 }
 
 // updateSelectedItem update the text of the selected item.