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 %}