title: select2 Maximum call stack exceeded on dependent dropdown
body: <p>i have tow dropdown the first one show the item by number ,and the second one show the item names so the user can select the item  by item number or by item name and if he select item number another dropdown will update selected value her is my code</p>
  
  <p>i create simple on change function to update another dropdown value</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$('.select').select2({
    "width":"100px"
  });
  
  
  $(document).on("change", "#block_name", function () {
    id = $(this).val();
    $("#block_number").select2('val',id);
  });
  
  $(document).on("change", "#block_number", function () {
    id = $(this).val();
    $("#block_name").select2('val',id);
  
  });</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css"&gt;
  
  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
  
  &lt;script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"&gt;&lt;/script&gt;
  
  &lt;select name="block" id="block_name" class="select"&gt;
    &lt;option value="1"&gt;1&lt;/option&gt;
    &lt;option value="2"&gt;2&lt;/option&gt;
    &lt;option value="3"&gt;3&lt;/option&gt;
    &lt;option value="4"&gt;4&lt;/option&gt;
    &lt;option value="5"&gt;5&lt;/option&gt;
  
  &lt;/select&gt;
  
  &lt;select name="block_number" id="block_number" class="select"&gt;
    &lt;option value="1"&gt;block1&lt;/option&gt;
    &lt;option value="2"&gt;block2&lt;/option&gt;
    &lt;option value="3"&gt;block3&lt;/option&gt;
    &lt;option value="4"&gt;block4&lt;/option&gt;
    &lt;option value="5"&gt;block5&lt;/option&gt;
  &lt;/select&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>any one could  help me i will appreciate  it </p>