Fatal error: Call to undefined function bp_activity_at_name_filter()

We got this error when we try to see the response of a question.
This line is the problem :

if($post->post_type == ‘answer’)
return bp_activity_at_name_filter($content);

I tried to add a “required_once” on the needed file, but it caused another problem.

See the related post to wordpress forum : https://wordpress.org/support/topic/fatal-error-call-to-undefined-function-bp_activity_at_name_filter-in?replies=4#post-6946351

I posted twice to also  keep this thread in this forum. It may be useful to others persons.

Could you give me a solution before you fix it in an update ?

Ty !