Major Steps to recreate:
1. Go to http://temp.zkfiddle.org:8080/t651/hjqomc/10/ (http://zkfiddle.org/sample/hjqomc/10-Failed-to-mount-Cannot-read-property-defaultView-of-null)
2. Click to Show button.
3. Close modal dialog with close button in title bar.
4. Click to Show button again.
5. Error console is shown.
Chrome error message
Failed to mount: Cannot read property 'defaultView' of null
Firefox error message
Failed to mount: elem.ownerDocument is null
Problem is caused by hflex attributes in inner.zul file:
inner.zul
<zk>
<window>
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
<grid>
<columns>
<column hflex="min">A</column>
<column hflex="min">B</column>
<column >C</column>
</columns>
<rows>
<row>
<label>1</label>
<label>2</label>
<label>3</label>
</row>
<row>
<label>a</label>
<label>b</label>
<div>c</div>
</row>
</rows>
</grid>
</window>
</zk>
