title: Unable to edit item after item selection in ng-select angular
body: <p>I am using <code>ng-select</code></p>
  
  <pre><code>https://www.npmjs.com/package/@ng-select/ng-select
  </code></pre>
  
  <p>npm library in my angular project. it is working with large data without any problem.</p>
  
  <p>But I am unable to edit the selected item and navigation keys are not working inside the input box once the item is selected.</p>
  
  <p>For example I searched <strong>something12</strong> first, then I had to choose <strong>something31</strong>. In this case I can't clear last two characters.
  To change the search thing, I have to clear whole text and retype again for new search.</p>
  
  <p><strong>Versions:</strong></p>
  
  <pre><code>ng-select 2.16.4
  angular 7.2.2
  </code></pre>