Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/d8a08a3e15f3
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 952533 - [Messages] The contact lookup fails in some situation r=rwaldron

* Bail out early if the current contact does not have the wanted field