Snapshot testing issue

### Description

While trying to snapshot test a component that uses the Table component from element-react, I'm getting the following error:

```
TypeError: Cannot read property 'clientWidth' of null
```

### Reproduce Steps

1. Create a component, that uses the Table component
2. Create a jest test with
```
it('renders correctly', () => {
const tree = renderer
.create()
.toJSON();
expect(tree).toMatchSnapshot();
});
```
3. This wil show the error above.

### Error Trace (if possible)

```

at TableLayout.caculateWidth (node_modules/element-react/dist/npm/es5/src/table/TableLayout.js:160:36)
at TableLayout.scheduleLayout (node_modules/element-react/dist/npm/es5/src/table/TableLayout.js:137:26)
at TableLayout.componentDidMount (node_modules/element-react/dist/npm/es5/src/table/TableLayout.js:81:12)
at commitLifeCycles (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:4553:24)
at commitAllLifeCycles (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:5729:9)
at HTMLUnknownElement.callCallback (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:1610:14)
at invokeEventListeners (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:219:27)
at HTMLUnknownElementImpl._dispatch (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:126:9)
at HTMLUnknownElementImpl.dispatchEvent (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:87:17)
at HTMLUnknownElementImpl.dispatchEvent (node_modules/jsdom/lib/jsdom/living/nodes/HTMLElement-impl.js:36:27)
at HTMLUnknownElement.dispatchEvent (node_modules/jsdom/lib/jsdom/living/generated/EventTarget.js:61:35)
at Object.invokeGuardedCallbackDev (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:1649:16)
at invokeGuardedCallback (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:1506:29)
at commitRoot (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:5833:9)
at performWorkOnRoot (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6800:42)
at performWork (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6750:7)
```

Did I miss something?

Thanks