TabBarView.removeTab throws NoSuchElementException if there are no tabs left in the tab bar

**Originally by _mvysny2_**

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Calling TabBarView.removeTab on the last tab fails:

```
java.util.NoSuchElementException
    at java.util.LinkedList$ListItr.next(LinkedList.java:890)
    at com.vaadin.addon.touchkit.ui.TabBarView.removeTab(TabBarView.java:124)
```

Touchkit 4.1.0.rc1

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 Imported from https://dev.vaadin.com/ issue #19499
