NC11 Activity App "Error PHP Array to string conversion" since upgrade from 10.0.2 to NC11

Hi , i noticed that there are php error messages in NC11 logfile since upgrade to NC 11 from NC 10.0.2.

Error PHP Array to string conversion at /var/www/nextcloud/apps/activity/lib/Formatter/BaseFormatter.php#35 2016-12-19T08:57:30+0100

Additional Information:
Im shure that these messages are only logged when i look to the activity from files wich are shared with other users.

Is there any way o fix this ?

Seeing the same thing since the upgrade to OC11.