title: cannot read property 'blur' of undefined?
body: <p>Using ref in Material-UI TextField as :-</p>
  
  <pre><code>&lt;TextField
   label="Select "
   value={this.state.type}
   inputRef={this.selectCar}
   type="text"
  /&gt;
  </code></pre>
  
  <p>Here selectCar is defined in constructor as :-</p>
  
  <pre><code>this.selectCar = React.createRef();
  </code></pre>
  
  <p>when doing </p>
  
  <pre><code>this.selectCar.current.blur;
  </code></pre>
  
  <p>it is giving error</p>
  
  <pre><code>cannot read property 'blur' of undefined?
  </code></pre>