The tests output contained following warning:
```
console.warn
Th: Table headers must have an accessible name. If the Th is intended to be visually empty, pass in screenReaderText. If the Th contains only non-text, interactive content such as a checkbox or expand toggle, pass in an aria-label.
```
This fixes the warning by adding an `aria-label` to every empty table heading cell.
8a25ec66f3