for the same reason as...

commit fb2c1467
Author: Eike Rathke <erack@redhat.com>
Date:   Mon Jul 25 13:32:17 2016 +0200

    use div() instead of /0 to content ubsan

    While we do handle double floating point division by 0 at least on
    IEEE754 systems, ubsan builds mock about.

Change-Id: I2c96b63a4af3cb2e8483a1d0f2da91ea82da227c