errors for WP ver3.6.1

I am getting multiple notices but also a warning:
Warning: trim() expects parameter 1 to be string, array given in /var/www/vhosts/blurtonline.com/httpdocs/wp-content/plugins/easy-nivo-slider/3rd-party/filosofo-custom-image-sizes.php on line 31

So I changes line 31 from:

$size_name = trim($size_name);

to

$size_name = trim('thumbnail');

It removed the warning.