React 16 alpha allows returning array in render function but server renderer expects children to always be react elements

```
TypeError: Cannot read property 'toLowerCase' of undefined
    at ReactDOMServerRenderer.renderDOM
```

source
```javascript
function renderDOM(element, context) {
    var tag = element.type.toLowerCase(); // element is array
```

Fiddle: https://jsfiddle.net/84v837e9/160/

**react@16.0.0-alpha.13**
},
      enqueueSetState: function(publicInstance, partialState) {
        if (queue === null) {
          warnNoop(publicInstance, 'setState');
          return null;
        }
        queue.push(partialState);
      },
    };
    if (shouldConstruct(Component)) {
      inst = new Component(child.props, publicContext, updater);
    } else {
      inst = Component(child.props, publicContext, updater);
      if (inst == null || inst.render == null) {
        child = inst;
        continue;
      }
    }
    inst.props = child.props;
    inst.context = publicContext;
    inst.updater = updater;
    var initialState = inst.state;
    if (initialState === undefined) {
      inst.state = initialState = null;
    }
    if (inst.componentWillMount) {
      inst.componentWillMount();
      if (queue.length) {
        var oldQueue = queue;
        var oldReplace = replace;