In some undetermined cases, when you click in a tag in a tag block, you can have this message :

> Exception : Call to a member function make_active() on bool

And I get the following log :

> Default exception handler: Exception : Call to a member function make_active() on boolean Debug: 
> Error code: generalexceptionmessage
> * line 84 of /tag/index.php: Error thrown

This happens on my production platform (moodle 3.9.16), but I have never found the conditions to meet to be able to reproduce it elsewhere.