webadmin: Coverity defect CID 1230097 (FB.BC_UNCONFIRMED_CAST)

Swapped unsafe cast for properly-parameterized event.

Change-Id: I2b42060e7b906b1172d1f823d63c6fbcf1703fdd
Signed-off-by: Lior Vernia <lvernia@redhat.com>