Steps to reproduce the issue

• Install Joomla 3.6.0-beta1
• Create a new article, click "Image" button in TinyMCE to insert an image into article's content, it works.

• Edit administrator/components/com_content/models/forms/article.xml, replace the "metakey" field from

  <field name="metakey" type="textarea"
      label="JFIELD_META_KEYWORDS_LABEL" description="JFIELD_META_KEYWORDS_DESC"
      rows="3" cols="30" />
  

to

    <field name="metakey" type="editor"
        label="JFIELD_META_KEYWORDS_LABEL" description="JFIELD_META_KEYWORDS_DESC"
        filter="JComponentHelper::filterText" buttons="true" />

• Refresh your article form, check in "Publishing" tab to see if "Meta Keywords" field now becomes a TinyMCE editor instead of textarea field

• Try to insert an image in "Meta Keywords" field or article content field, the image popup is not closed after you click "Insert" button. If you check in browser's developer tool, there is an error , for Chrome it is "Uncaught RangeError: Maximum call stack size exceeded", for Firefox it is "too much recursion", the code causes this problem is

      jModalClose = function() {
          oldClose.apply(this, arguments);
          tinyMCE.activeEditor.windowManager.close();
      };
  

Expected result

Image is inserted into TinyMCE editor and the image popup is closed, no matter how many TinyMCE editors are available on the page.

Actual result

Image is inserted successfully but image popup is not closed.

System information (as much as possible)

• Joomla! Version: Joomla! 3.6.0-beta1 Beta [ Noether ] 8-June-2016 23:13 GMT
• Joomla! Platform Version: Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
• Tried on Chrome 51.0.2704.84 and Firefox 45.1.1

Additional comments