GabblePresenceCache: _process_caps: don't free uninitialized pointer if presence is NULL
GabblePresenceCache: _process_caps: don't free uninitialized pointer if presence is NULL

jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble