title: Error trying to diff 'xx01'. Only arrays and iterables are allowed
body: <p>Suppose I'm receiving from an API an array of strings like ["xx01","xx02","xx03",..]. Which changes I should do here to have an autocomplete list (primeng) which works correctly.</p>
  
  <p>I have this message error : ERROR Error: Error trying to diff 'xx02'. Only arrays and iterables are allowed</p>
  
  <pre><code>export class TaskComponent {
  
  public sales: string[];
  sale_A : string;
  form: FormGroup;
  
  constructor(private customer: CustomerService, private fb: FormBuilder, private router: Router) {
  }
  
  ngOnInit() {
      this.customer.getSales().subscribe(result =&gt; {
          this.sales = result;
          console.log(this.sales);
      });
      this.buildForm();
  }
  
  onSelectSale(event) {
      this.sales = event;
  }
  
  searchSales(event) {
      this.customer.getSales().subscribe(result =&gt; {
          this.sales = result;
      });
  }
  
  buildForm() {
      this.form = this.fb.group({
          sale_A: [{ value: ''}, Validators.required],
          sale_B: [{ value: '', disabled: true }, Validators.required]
      });
  }
  </code></pre>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div class="col-md-5"&gt;
                  &lt;p-autoComplete formControlName="sale_A"
                                  inputStyleClass="form-control"
                                  [dropdown]="true"
                                  [(ngModel)]="sales"
                                  [suggestions]="sales"
                                  (onDropdownClick)="searchSales($event)"
                                  (completeMethod)="searchSales($event)"
                                  (onSelect)="onSelectSale($event)"
                                  emptyMessage="no msg"&gt;
                      &lt;ng-template let-title pTemplate="item"&gt;
                          &lt;p&gt;{{sales[0] | json}}&lt;/p&gt;
                      &lt;/ng-template&gt;
                  &lt;/p-autoComplete&gt;
              &lt;/div&gt;
  </code></pre>