log-format-json throws panic in v0.5.0

[montaguethomas]

Describe the bug
When trying to use the -log-format-json=true flag, kms panics:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xafb309]

goroutine 1 [running]:
k8s.io/component-base/logs/json.(*nopSync).Write(0x8?, {0xc0000fec00?, 0x0?, 0xc9a865?})
	<autogenerated>:1 +0x29
go.uber.org/zap/zapcore.(*lockedWriteSyncer).Write(0xc000352990, {0xc0000fec00?, 0x23348a0?, 0x12a8c20?})
	/go/pkg/mod/go.uber.org/[email protected]/zapcore/write_syncer.go:66 +0x72
go.uber.org/zap/zapcore.(*ioCore).Write(0xc00031d260, {0x0, {0xc1461a375222ccdc, 0x23348a0, 0x12a8c20}, {0x0, 0x0}, {0xc9df10, 0xf}, {0x1, ...}, ...}, ...)
	/go/pkg/mod/go.uber.org/[email protected]/zapcore/core.go:99 +0xb5
go.uber.org/zap/zapcore.(*CheckedEntry).Write(0xc00035a1a0, {0xc000364000, 0x2, 0x2})
	/go/pkg/mod/go.uber.org/[email protected]/zapcore/entry.go:255 +0x1d9
github.com/go-logr/zapr.(*zapLogger).Info(0xc00031d2f0, 0x0, {0xc9df10?, 0x5a3522?}, {0xc0003564e0, 0x2, 0x2})
	/go/pkg/mod/github.com/go-logr/[email protected]/zapr.go:210 +0xa5
github.com/go-logr/logr.Logger.Info({{0xdc20c8?, 0xc00031d2f0?}, 0x0?}, {0xc9df10, 0xf}, {0xc0003564e0, 0x2, 0x2})
	/go/pkg/mod/github.com/go-logr/[email protected]/logr.go:278 +0xe4
k8s.io/klog/v2.(*loggingT).infoS(0x3?, 0x20?, {0x0?, 0x0?}, 0xc00025dad0?, {0xc9df10?, 0xdbd568?}, {0xc0003564e0, 0x2, 0x2})
	/go/pkg/mod/k8s.io/klog/[email protected]/klog.go:780 +0x113
k8s.io/klog/v2.InfoS(...)
	/go/pkg/mod/k8s.io/klog/[email protected]/klog.go:1512
github.com/Azure/kubernetes-kms/pkg/metrics.InitMetricsExporter({0xc9a865, 0xa}, {0xc9472b, 0x4})
	/workspace/pkg/metrics/exporter.go:17 +0xf6
main.main()
	/workspace/main.go:82 +0x195

Steps To Reproduce
/kubernetes-kms -log-format-json=true

Expected behavior
Does not panic

KMS Plugin for Key Vault version
v0.5.0

Kubernetes version
v1.26.9

[aramase]

@nilekhc could you take a look at this?