Upgrade from 4.2.2 to 4.2.4 stuck while upgrading machine-config operator

Issue

• Machine config controller is crashing or panicking and printing out the following:

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xe60bf5]

goroutine 257 [running]:
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/runtime.HandleCrash(0x0, 0x0, 0x0)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/runtime/runtime.go:58 +0x108
panic(0x15aec80, 0x28dbcd0)
    /opt/rh/go-toolset-1.11/root/usr/lib/go-toolset-1.11-golang/src/runtime/panic.go:513 +0x1b9
github.com/openshift/machine-config-operator/pkg/apis/machineconfiguration.openshift.io/v1.(*MachineConfigPool).GetNamespace(0x0, 0x0, 0x19e98a0)
    <autogenerated>:1 +0x5
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.MetaNamespaceKeyFunc(0x1778ea0, 0x0, 0xc0005669c0, 0x1528080, 0xc000c75630, 0x12a05f200)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/store.go:84 +0x114
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.DeletionHandlingMetaNamespaceKeyFunc(0x1778ea0, 0x0, 0xc000c75630, 0x12a05f200, 0x0, 0x0)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/controller.go:261 +0x6a
github.com/openshift/machine-config-operator/pkg/controller/node.(*Controller).enqueueAfter(0xc000562140, 0x0, 0x12a05f200)
    /go/src/github.com/openshift/machine-config-operator/pkg/controller/node/node_controller.go:604 +0x41
github.com/openshift/machine-config-operator/pkg/controller/node.(*Controller).enqueueDefault(0xc000562140, 0x0)
    /go/src/github.com/openshift/machine-config-operator/pkg/controller/node/node_controller.go:615 +0x44
github.com/openshift/machine-config-operator/pkg/controller/node.(*Controller).enqueueDefault-fm(0x0)
    /go/src/github.com/openshift/machine-config-operator/pkg/controller/node/node_controller.go:125 +0x34
github.com/openshift/machine-config-operator/pkg/controller/node.(*Controller).addNode(0xc000562140, 0x1794e00, 0xc0003672c0)
    /go/src/github.com/openshift/machine-config-operator/pkg/controller/node/node_controller.go:397 +0x1a1
github.com/openshift/machine-config-operator/pkg/controller/node.(*Controller).addNode-fm(0x1794e00, 0xc0003672c0)
    /go/src/github.com/openshift/machine-config-operator/pkg/controller/node/node_controller.go:115 +0x3e
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.ResourceEventHandlerFuncs.OnAdd(0xc0003380b0, 0xc0003380c0, 0xc0003380d0, 0x1794e00, 0xc0003672c0)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/controller.go:195 +0x49
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.(*processorListener).run.func1.1(0x0, 0xc0009ae000, 0xc00095c190)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/shared_informer.go:554 +0x21d
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.ExponentialBackoff(0x989680, 0x3ff0000000000000, 0x3fb999999999999a, 0x5, 0x0, 0xc000963e18, 0x429692, 0xc00095c1c0)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:265 +0x51
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.(*processorListener).run.func1()
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/shared_informer.go:548 +0x79
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.JitterUntil.func1(0xc00099b768)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:152 +0x54
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.JitterUntil(0xc000963f68, 0xdf8475800, 0x0, 0x1582101, 0xc000766180)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:153 +0xbe
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.Until(0xc00099b768, 0xdf8475800, 0xc000766180)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:88 +0x4d
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.(*processorListener).run(0xc00035c500)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/shared_informer.go:546 +0x8d
github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache.(*processorListener).run-fm()
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/client-go/tools/cache/shared_informer.go:390 +0x2a
github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.(*Group).Start.func1(0xc000452060, 0xc0009ac000)
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:71 +0x4f
created by github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait.(*Group).Start
    /go/src/github.com/openshift/machine-config-operator/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:69 +0x62

Unable to apply 4.2.4: timed out waiting for the condition during waitForControllerConfigToBeCompleted: controllerconfig is not completed: status for ControllerConfig machine-config-controller is being reported for 2, expecting it for 3