Angularjs ng-show/ng-if not working properly for images

Question

I am getting Image dynamically if image with that name is present in that folder then image should be visible if no image in folder image tag must be hidden, for that I used ng-show/ng-if but some times it hides if no image in folder and some time it don't hides if no image in folder.I used both ng-if and ng-show but no luck.

here is my sample code

<tr ng-repeat="team in teams">
    <td>
       <span ng-if="img/gflag/{{team._id}}.png">
         <img  ng-src="img/gflag/{{team._id}}.png">
       </span>
     </td>
  </tr>


    <tr ng-repeat="team in teams">
      <td>
       <span ng-show="img/gflag/{{team._id}}.png">
         <img  ng-src="img/gflag/{{team._id}}.png">
       </span>
     </td>
    </tr>