How to display an empty value in the opencart basket and make it count correctly?

Question

JavaScript

Hello, in opencart 2.1.0.1 I made the basket an icon, when adding a product, the counter works correctly shows 1, 2 or 3 products on the basket, etc., when at least one product is deleted, the number disappears and if there were 3, for example, then the number 2 does not appear , also does not show 0 when the cart is empty.
If in this function I do 0

setTimeout(function () {
          if (json['count'] != null) {
                        $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png"><span class="count">' + json['count'] + '</span>');
                    } else {
                        $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png">');
                    }
        }, 100);

Then an inscription appears

if I write null, then it disappears along with a yellow circle where 0 should be displayed. Could you help and tell me what should be added so that the values ​​\u200b\u200bare correctly processed.
Full code for cart functions from common.js file

var cart = {
  'add': function(product_id, quantity) {
    $.ajax({
      url: 'index.php?route=checkout/cart/add',
      type: 'post',
      data: 'product_id=' + product_id + '&quantity=' + (typeof(quantity) != 'undefined' ? quantity : 1),
      dataType: 'json',
      beforeSend: function() {
        $('#cart > button').button('loading');
      },
      complete: function() {
        $('#cart > button').button('reset');
      },
      success: function(json) {
        $('.alert, .text-danger').remove();

        if (json['redirect']) {
          location = json['redirect'];
        }

        if (json['success']) {
          $('#content').parent().before('<div class="alert alert-success"><i class="fa fa-check-circle"></i> ' + json['success'] + ' <button type="button" class="close" data-dismiss="alert">&times;</button></div>');

          // Need to set timeout otherwise it wont update the total
          setTimeout(function () {
            $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png"><span class="count">' + json['count'] + '</span>');
          }, 100);

          $('html, body').animate({ scrollTop: 0 }, 'slow');

          $('#cart > ul').load('index.php?route=common/cart/info ul li');
        }
      },
          error: function(xhr, ajaxOptions, thrownError) {
              alert(thrownError + "\r\n" + xhr.statusText + "\r\n" + xhr.responseText);
          }
    });
  },
  'update': function(key, quantity) {
    $.ajax({
      url: 'index.php?route=checkout/cart/edit',
      type: 'post',
      data: 'key=' + key + '&quantity=' + (typeof(quantity) != 'undefined' ? quantity : 1),
      dataType: 'json',
      beforeSend: function() {
        $('#cart > button').button('loading');
      },
      complete: function() {
        $('#cart > button').button('reset');
      },
      success: function(json) {
        // Need to set timeout otherwise it wont update the total
        setTimeout(function () {
          $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png"><span class="count">' + json['count'] + '</span>');
        }, 100);

        if (getURLVar('route') == 'checkout/cart' || getURLVar('route') == 'checkout/checkout') {
          location = 'index.php?route=checkout/cart';
        } else {
          $('#cart > ul').load('index.php?route=common/cart/info ul li');
        }
      },
          error: function(xhr, ajaxOptions, thrownError) {
              alert(thrownError + "\r\n" + xhr.statusText + "\r\n" + xhr.responseText);
          }
    });
  },
  'remove': function(key) {
    $.ajax({
      url: 'index.php?route=checkout/cart/remove',
      type: 'post',
      data: 'key=' + key,
      dataType: 'json',
      beforeSend: function() {
        $('#cart > button').button('loading');
      },
      complete: function() {
        $('#cart > button').button('reset');
      },
      success: function(json) {
        // Need to set timeout otherwise it wont update the total
        setTimeout(function () {
          if (json['count'] != null) {
                        $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png"><span class="count">' + json['count'] + '</span>');
                    } else {
                        $('#cart > button').html('<img src="catalog/view/theme/kam/image/cart.png">');
                    }
        }, 100);

        if (getURLVar('route') == 'checkout/cart' || getURLVar('route') == 'checkout/checkout') {
          location = 'index.php?route=checkout/cart';
        } else {
          $('#cart > ul').load('index.php?route=common/cart/info ul li');
        }
      },
          error: function(xhr, ajaxOptions, thrownError) {
              alert(thrownError + "\r\n" + xhr.statusText + "\r\n" + xhr.responseText);
          }
    });
  }
}

var voucher = {
  'add': function() {

  },
  'remove': function(key) {
    $.ajax({
      url: 'index.php?route=checkout/cart/remove',
      type: 'post',
      data: 'key=' + key,
      dataType: 'json',
      beforeSend: function() {
        $('#cart > button').button('loading');
      },
      complete: function() {
        $('#cart > button').button('reset');
      },
      success: function(json) {
        // Need to set timeout otherwise it wont update the total
        setTimeout(function () {
          $('#cart > button').html('<img src="catalog/view/theme/default/image/cart.png"><span class="count">' + json['count'] + '</span>');
        }, 100);

        if (getURLVar('route') == 'checkout/cart' || getURLVar('route') == 'checkout/checkout') {
          location = 'index.php?route=checkout/cart';
        } else {
          $('#cart > ul').load('index.php?route=common/cart/info ul li');
        }
      },
          error: function(xhr, ajaxOptions, thrownError) {
              alert(thrownError + "\r\n" + xhr.statusText + "\r\n" + xhr.responseText);
          }
    });
  }
}