frontend User: error while creating group

[janc]

when I try to create a group, afte rdefining properties, I get the error message
Fatal error: Call to undefined function: rowcount() in /home/h2760het/public_html/cmsms/modules/FrontEndUsers/FrontEndUsers.api.php on line 1477

I use the most recent versions of CMSMS and FrontEnd User.

I can't find this error on the forum.

Hope someone can help me.

Greetings
Jan.C