Argument #1 is not an array warning

Hello,

When I run a search query in my site this warning appear :

Warning: array_merge(): Argument #1 is not an array in /home/mysite/www/mytheme/wp-content/plugins/pmpro-bbpress/pmpro-bbpress.php on line 206

Regards
The x Learner

https://ww.wp.xz.cn/plugins/pmpro-bbpress/