This might be a reference to this one: https://github.com/facebook/react/issues/10212#issuecomment-346302374

The problem still exist.

So, trying to render with server side and got this error. I don't have this notation in my code but this might be a problem with dependencies.

```
TypeError: Cannot read property 'toLowerCase' of undefined
    at ReactDOMServerRenderer.renderDOM (/Users/lukasborawski/Dev/web-client/node_modules/react-dom/cjs/react-dom-server.node.development.js:2304:27)
...
```

```
"react": "^16.1.1",
"react-dom": "^16.2.0",
```

Thx for help.
const innerHTML = props.dangerouslySetInnerHTML;
  if (innerHTML != null) {
    if (innerHTML.__html != null) {
      return innerHTML.__html;
    }
  } else {
    const content = props.children;
    if (typeof content === 'string' || typeof content === 'number') {
      return escapeTextForBrowser(content);
    }
  }
  return null;
}
function flattenTopLevelChildren(children: mixed): FlatReactChildren {
  if (!React.isValidElement(children)) {
    return toArray(children);
  }
  const element = ((children: any): ReactElement);
  if (element.type !== REACT_FRAGMENT_TYPE) {
    return [element];
  }
  const fragmentChildren = element.props.children;
  if (!React.isValidElement(fragmentChildren)) {
    return toArray(fragmentChildren);
  }
  const fragmentChildElement = ((fragmentChildren: any): ReactElement);
  return [fragmentChildElement];
}
function flattenOptionChildren(children: mixed): string {