Catch zone import id being None in POST response.

the linked issue suggests that it is possible for zone import id to
be None right upon creation. While I was not able to reproduce this,
let's add an explicit catch for it to make such sutuation more obvious
when this happens again.

Change-Id: I1add5caa29a1ebaf789b1d1123b385de3bf6678d
Related-Issue: PRODX-39453
1 file changed