Steps to reproduce the issue

• create a new user
• verify, that the user is member of public
• now select this user and push button "batch"
• In the dialog select "public" as group, activate option "delete from group" and password option "no action"
• execute

Expected result

an error message like "the user must be member of at least one group"

Actual result

the batch is done and the user is member of no group

System information (as much as possible)

seen with J3.9.25

Additional comments

creating a new user will not allow this, so the message text from there is usable ;-)