Widjet Question

Dear Users.
I have a question, on the widjet display i′m getting the following error:

Warning: Invalid argument supplied for foreach() in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 186

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 230

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 258

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 277

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 305

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 306

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 307

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 308

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 343

Warning: in_array() expects parameter 2 to be array, null given in /homepages/30/d554795221/htdocs/clickandbuilds/car2show/wp-content/plugins/likebtn-like-button/likebtn_like_button_most_liked_widget.class.php on line 372
No items liked yet.

I ask for help.
Secondly, where do I get my API Key?
Site: CAR2SHOW

Thanks in advance.