WP image upload not returning URL

I want an image upload in my widget.
The WP image upload screen pops up like it should but when i choose an image, the url is not returned to the textfield. Any idea why?

php :

// queue up the necessary js
function hrw_enqueue()
{
  wp_enqueue_style('thickbox');
  wp_enqueue_script('media-upload');
  wp_enqueue_script('thickbox');
  // moved the js to an external file, you may want to change the path
  wp_enqueue_script('hrw', plugin_dir_url( __FILE__ ).'js/uploadimg.js', null, null, true);
}
add_action('admin_enqueue_scripts', 'hrw_enqueue');

html

 <p>
      <label for="<?php echo $this->get_field_id('image_uri'); ?>">Image</label><br />
      <input type="text" class="img" name="<?php echo $this->get_field_name('image_uri'); ?>" id="<?php echo $this->get_field_id('image_uri'); ?>" value="<?php echo $instance['image_uri']; ?>" />
      <input type="button" class="select-img" value="Select Image" />
    </p>

js file :

jQuery( document ).ready(function() {
	var image_field;
jQuery(function($){
  $(document).on('click', 'input.select-img', function(evt){
    image_field = $(this).siblings('.img');
    tb_show('', 'media-upload.php?type=image&TB_iframe=true');
    return false;
  });
  window.send_to_editor = function(html) {
    imgurl = $('img', html).attr('src');
    image_field.val(imgurl);
    tb_remove();
  }
});

});