Tooltips sometimes do not appear
Reported via https://vaadin.com/directory/component/tooltips4vaadin/discussions
```
<java.version>1.8</java.version>
<vaadin.version>14.7.2</vaadin.version>
```
```
@Route
public class MainView extends VerticalLayout {
public MainView() {
for (int i = 0; i < 10; i++) {
Button myButton = new MyButton();
Button show = new Button("Show", e -> myButton.setVisible(true));
add(new HorizontalLayout(show, myButton));
}
}
private static class MyButton extends Button implements HasTooltip {
public MyButton() {
setIcon(VaadinIcon.VAADIN_H.create());
setTooltip("Tooltip");
setVisible(false);
}
}
}
```
issue