PHP Warning: session_start()

Hello
I’m talking about a website with nothing else than Enfold (no plugins, etc.)

I have disable the cron tasks and they are run each 6 hours like described here: http://www.inmotionhosting.com/support/website/wordpress/disabling-the-wp-cronphp-in-wordpress

So here an exemple how I run the cron tasks: cd /home/maquetta/gueze-sas.fr; php -q wp-cron.php
It works nice and I have 16 websites configured like this but only the one using Enfold return an alert in error_log like this:
[04-Apr-2017 16:00:08 UTC] PHP Warning: session_start(): Cannot send session cookie – headers already sent in /home/maquetta/gueze-sas.fr/wp-content/themes/enfold/config-templatebuilder/avia-shortcodes/masonry_entries.php on line 33

And yes there is something about session in this file line 33:

function extra_assets()
			{
				add_action('wp_ajax_avia_ajax_masonry_more', array('avia_masonry','load_more'));
				add_action('wp_ajax_nopriv_avia_ajax_masonry_more', array('avia_masonry','load_more'));
				
				if(!is_admin() && !current_theme_supports('avia_no_session_support') && !session_id()) session_start();
			}

Any ideas?

Thanks