title: Cannot read property 'touched' of null Angular 2
body: <p>I have this error all the time when create a new input in my page, I don't know why and I loose a lot of time on it without solve. Anyone can help?</p>
  
  <ol>
  <li><p>Follow my HTML:</p>
  
  <pre><code>&lt;div class="form-group"
          [ngClass]="{'has-error': (customerForm.get('rating').touched || 
                                    customerForm.get('rating').dirty) &amp;&amp; 
                                    !customerForm.get('rating').valid }"&gt;
      &lt;label class="col-md-2 control-label" 
              for="ratingId"&gt;Rating&lt;/label&gt;
  
      &lt;div class="col-md-8"&gt;
           &lt;input class="form-control" 
                     id="ratingId" 
                     type="number" 
                     formControlName = "rating" /&gt;
           &lt;span class="help-block" *ngIf="(customerForm.get('rating').touched 
                                               || customerForm.get('rating').dirty) &amp;&amp; 
                                               customerForm.get('rating').errors"&gt;
              &lt;span *ngIf="customerForm.get('rating').errors.range"&gt;
                  Please rate your experience from 1 to 5.
              &lt;/span&gt;
           &lt;/span&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre></li>
  <li><p>I already created my 'rating' in FormBuilder:</p>
  
  <pre><code>ngOnInit(): void {
  this.customerForm = this.formBuilder.group({
      firstName: ['', [Validators.required, Validators.minLength(3)]],
      lastName: ['', [Validators.required, Validators.maxLength(50)]],
      phone: '',
      rating: '',
      notification: 'email',
      sendCatalog: true
    });
  }
  </code></pre></li>
  </ol>
  
  <p>I also tried to use the <strong>"safe navigation operator"</strong> in all places where I am calling the ('rating') name in the HTML but, when tried it returns the follow error in the console:
  Cannot find control with name: 'rating'</p>
  
  <ul>
  <li>Remembering that this control is already defined in my FormBuilder and in the HTML (formControlName).</li>
  </ul>