QuickViewContent render() may return empty content with attached views on the default tab.

Quicktabs 7.x-3.4
Views 7.x-3.5

Example/Step to reproduce :
* Create a view with 2 displays blocks "list" and "list first"
** add some filters so the view will return only 1 item.
** "list" should have pagination option set to "skip 1" element.
** "list first" should have pagination option set to only "show 1" element.
** in "list" attach "list first" as a view header zone (attachment).

* Create a quicktabs with 2 tabs, both tabs set to display the previously created view "list"
** Set the option to only preload the first tab.

Now, embed the Quicktab somewhere and check the results :

The first tab (preloaded) is empty.
The second tab (ajax) shows 1 item.

The problem is with "attached" views, $view->preview() will return some valid markup, but will not fill $view->result if the "main view" has no results, even tho the attached views got some results. The render() code in Quicktabs will believe there is nothing to display.

The second (ajax) tab will show results because it does not execute the same code (goes thru views_ajax();)