500 Error: "foreach" array problem?

Hello, we are having a problem on one of our websites: https://www.yourpoolservice.net where a 500 server error will appear in many cases when navigating around the wp-admin dashboard, and also on the front end of the site. This does not happen all the time, but now is more frequent.

Here are the errors found:
PHP Warning: Invalid argument supplied for foreach() in…. – helper-assets.php on line 327

/**
	* Checks the entries for the current page for av_video, av_audio, <audio>, <video> and background video elements. 
	*
	* @since 4.3
	* @added_by Kriesi
	* @param array $assets
	*/
	function av_video_assets_required() 
	{
		global $posts;
		
		$used 	= false;
		$regex 	= "!\[av_blog|\[av_postslider|\[av_video|\[av_audio|\[av_player|\[audio|<audio|<video|video\=\'http|video\=\"http!";
		
#Line 327	foreach($posts as $post)
		{
			preg_match($regex, $post->post_content, $matches);
			
			if(isset($matches[0]) )
			{
				$used = true;
				break;
			}
			
			$format = get_post_format( $post->ID );
			
			if($format == "audio" || $format == "video")
			{
				$used = true;
				break;
			}
		}
		
		return $used;
	}
}

if( ! function_exists( 'av_slideshow_required' ) )
{