fix: panic on shutdown

Fixes #9017

Don't assume the config is there before trying to access it.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>
(cherry picked from commit d983e44)

internal/app/machined/pkg/runtime/v1alpha1/v1alpha1_sequencer.go

@@ -376,11 +376,13 @@ func (*Sequencer) Reset(r runtime.Runtime, in runtime.ResetOptions) []runtime.Ph
 
 // Shutdown is the shutdown sequence.
 func (*Sequencer) Shutdown(r runtime.Runtime, in *machineapi.ShutdownRequest) []runtime.Phase {
+	skipNodeRegistration := r.Config() != nil && r.Config().Machine() != nil && r.Config().Machine().Kubelet().SkipNodeRegistration()
+
 	phases := PhaseList{}.Append(
 		"storeShudown",
 		StoreShutdownEmergency,
 	).AppendWhen(
-		!in.GetForce() && !r.Config().Machine().Kubelet().SkipNodeRegistration(),
+		!in.GetForce() && !skipNodeRegistration,
 		"drain",
 		CordonAndDrainNode,
 	).Append(