image-reflector-controller segfault on bad semver range

[EricHorst]

Describe the bug

When this ImagePolicy was deployed, the image-reflector-controller started crashlooping with the error that follows. Taking the second wildcard out of the range: value stopped the segfault crashloop.

apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImagePolicy
metadata:
  name: our-policy
  namespace: default 
spec:
  imageRepositoryRef:
    name: favorite-repo
  policy:
    semver:
      range: "*-*"

Log output:

2021-09-17 13:54:43.239 PDTpanic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x1657475] goroutine 334 [running]: github.com/fluxcd/image-reflector-controller/internal/policy.(*SemVer).Latest(0x0, 0xc000a5b8c0, 0x6, 0x6, 0x6, 0x6, 0x0, 0x0) /workspace/internal/policy/semver.go:55 +0x135 github.com/fluxcd/image-reflector-controller/controllers.(*ImagePolicyReconciler).Reconcile(0xc000458cd0, 0x1c00e18, 0xc001143c50, 0xc000a86c40, 0x7, 0xc0009aad80, 0x13, 0xc001143c00, 0x0, 0x0, ...) /workspace/controllers/imagepolicy_controller.go:146 +0x125a sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc000a237c0, 0x1c00d70, 0xc00092e380, 0x182d140, 0xc000aaefc0) /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.5/pkg/internal/controller/controller.go:298 +0x30d sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc000a237c0, 0x1c00d70, 0xc00092e380, 0x442700) /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.5/pkg/internal/controller/controller.go:253 +0x205 sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2(0xc000c51420, 0xc000a237c0, 0x1c00d70, 0xc00092e380) /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.5/pkg/internal/controller/controller.go:214 +0x6b created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2 /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.5/pkg/internal/controller/controller.go:210 +0x425

Steps to reproduce

1. deploy an ImagePolicy with semver range "-"
2. image-reflector-controller crashes

Expected behavior

No crash.

Screenshots and recordings

No response

OS / Distro

GKE 1.20

Flux version

0.17.0

Flux check

N/A

Git provider

No response

Container Registry provider

No response

Additional context

No response

Code of Conduct

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