After calling in Twig template:

{% if not ez_is_field_empty(content, 'main_image'') %}

{{ ez_render_field( content, 'main_image',

{ 'template': 'AppBundle:Field:ezimage_simple.html.twig' }

) }}

{% endif %}

i receive exception:
An exception has been thrown during the rendering of a template ("Notice: Trying to get property of non-object") in AppBundle:eZViews/full:samplepage.html.twig at line 91.

Line 91 contains if statement with not ez_is_field_empty(...)

symfony/symfony: v2.8.3
ezsystems/ezpublish-kernel: v6.1.1
ezsystems/ezpublish-legacy: v2015.01.3