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.
out += '\n';
      }
      out += innerMarkup;
    } else {
      children = toArray(props.children);
    }
    const frame = {
      domNamespace: getChildNamespace(parentNamespace, element.type),
      type: tag,
      children,
      childIndex: 0,
      context: context,
      footer: footer,
    };
    if (__DEV__) {
      ((frame: any): FrameDev).debugElementStack = [];
    }
    this.stack.push(frame);
    this.previousWasTextNode = false;
    return out;
  }
}
export default ReactDOMServerRenderer;