Version 2.0 has problems on admin pages

Hey!

I have just upgraded to version 2.0 and all admin pages have following error on top:

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 54

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 70

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 86

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 54

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 70

Warning: json_encode() expects exactly 1 parameter, 2 given in /home/tomiak/public_html/vanillaisland.pl/wp-content/plugins/wp-ulike/admin/classes/class-charts.php on line 86

I use WordPress 4.1, but same issue was on 4.0.1. Could you please help me get rid of those errors?

Here is the list of all other plugins I use:
Akismet 3.0.4 (active)
All In One SEO Pack 2.2.5.1 (active)
Disqus Comment System 2.84 (active)
Enhanced Media Library 2.0.3 (active)
Facebook Thumb Fixer 1.4.9 (active)
Like Button Voting & Rating 2.1.2
Shortcodes Ultimate 4.9.3 (active)
WP Social Icons 1.1 (active)
WP ULike 2.0 (active)

https://ww.wp.xz.cn/plugins/wp-ulike/