Unset debug-sender log handler before unreffing the global debug sender
Unset debug-sender log handler before unreffing the global debug sender

Otherwise, TpProxy destruction messages triggered by the death of the
global debug sender (as it probably holds the last ref to the
TpDBusDaemon) will be debug-logged through our custom log handler, which
asserts that the global debug sender still exists!

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