When deleting user, following error appeared (on next page):
Notice in ./server_privileges.php#384 Undefined variable: hostname Backtrace ./server_privileges.php#384: PMA_Error_Handler->handleError( integer 8, string Undefined variable: hostname, string /srv/http/pma.cihar.com/master-config/server_privileges.php, integer 384, array, )
Also it looks like backtrace information is quite wrong...
Actually there are two errors, second one being:
Cannot reproduce, but see https://github.com/phpmyadmin/phpmyadmin/pull/147.
Fix confirmed on demo server.