I encountered this bug in a Display suite 2-column lay-out where I wanted the left region to disappear when empty. 

Copy the template file to your theme's /templates folder and change:

{% if left %}

to

{% if left|render %}

It is sugested that turning off twig debugging also fixes this, but for me this was not the case.

Update July 2018

After re-encountering this issue, but now in general twig theming, the following snippet finally did the trick:

{% if page.sidebar_first|render|trim %}