Error while adding new category

Tag group plugin is excellent as it allows me to group the tags even when tags do not have hierarchy feature.

However, whenever I try to add a new category I get this following error:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /home/goleor/public_html/danapredict.com/wp-includes/taxonomy.php on line 2367

Warning: Cannot modify header information - headers already sent by (output started at /home/goleor/public_html/danapredict.com/wp-includes/taxonomy.php:2367) in /home/goleor/public_html/danapredict.com/wp-includes/class-wp-ajax-response.php on line 129

And when I deactivate Tag Groups plugin, there is no error while adding category. So the problem seems to be some kind of conflicting codes in Tag Groups plugin.

You may please note that I have following settings for Tag Groups plugin:

Taxonomy – post-tag
Theme – ui-darkness
Use Jquery – checked
Further options – Collapsible tags (checked)

And, this is how I am calling it in archives.php

if ( function_exists( 'tag_groups_cloud' ) ) echo tag_groups_cloud( array( 'smallest' => '13','largest' => '13','amount'=>'99' ) );

Given these settings, Category taxonomy should not be affected because I am using post_tag for Tag Groups. I wonder why it is happening.

Can someone suggest how to fix the error while adding a new category?

Many thanks.

https://www.ads-software.com/extend/plugins/tag-groups/