NullPointerException in web TabSheet implementation

[dtsaryov]

A topic on support forum: link.

Environment

• Platform version: 6.9.0

• Client type: Web

Description of the bug or enhancement

Setup test screen in the following way:

<button caption="Remove tabs"
        invoke="removeTabs"/>
<tabSheet id="tabsheet">
    <tab id="tab1"
         caption="tab1">
        <label value="Tab 1"/>
    </tab>
    <tab id="tab2"
         caption="tab2">
        <label value="Tab 2"/>
    </tab>
</tabSheet>

@Inject
private TabSheet tabsheet;

@Override
public void init(Map<String, Object> params) {
    tabsheet.addSelectedTabChangeListener(event -> {
        showNotification("Tab changed" + event.getSelectedTab());
    });
}

public void removeTabs() {
    tabsheet.removeAllTabs();
}

Open test screen and click the button.