Image validation not working

See more:

AngularJs

i am using directive for image validation like below

app.directive('validFile',function(){
  return {
    require:'ngModel',
    link:function(scope,el,attrs,ngModel){
      //change event is fired when file is selected
      el.bind('change',function(){
        scope.$apply(function(){
          ngModel.$setViewValue(el.val());
          ngModel.$render();
        });
      });
    }
  }
});

Quote:

before upload any image validation is working fine but when i click submit button after i removed image,image required validation is not working

my view page code is like below

<div class="fileupload-new thumbnail" id="fileupload-new" style="width:175px; height:120px;" ng-show="!filmstrip.tmp_base_creative">
    <img src="http://www.placehold.it/175x120/EFEFEF/AAAAAA&text=no+image" />
</div>
<div id="preview_image" class="fileupload-preview  thumbnail base_creative" style="max-width: 200px; max-height: 150px; line-height: 20px;" ng-show="filmstrip.base_creative">
    <img style="max-width: 200px; max-height: 150px;" src="<?php echo $this->config->item('creative_path');?>{{filmstrip.base_creative}}" />
</div>
<div>
    <span class="btn btn-file">
        <span class="fileupload-new" onclick="$('#base_creative').click()"><?php echo $this->lang->line('select_image');?></span>
        <span class="fileupload-exists" onclick="$('#base_creative').click()">Change</span>
        <input type="file" name="base_creative" id="base_creative" ng-model="filmstrip.base_creative" valid-file required required-message="'Creative is required'" onchange="angular.element(this).scope().getMobileImages(this.files,'base_creative',320,50);" />
    </span>
    <a ng-click="remove_image('tmp_base_creative',filmstrip.tmp_base1_creative)" class="btn fileupload-exists" data-dismiss="fileupload">Remove</a>
</div>

What I have tried:

first time when file is empty if i click submit button it shows error but once upload image and remove it from temporary folder i am not getting validation error if i click submit button even it does not have any value