Reverts the effect of a previous call to
g_object_freeze_notify(). The freeze count is decreased on
and when it reaches zero, queued “notify” signals are emitted.
Duplicate notifications for each property are squashed so that at most one
GObject::notify signal is emitted for each property, in the reverse order
in which they have been queued.
It is an error to call this function when the freeze count is zero.