Fix enabling & disabling addons with non-existing cluster

[spowelljr]

Fixes #17317

Enabling Addon

Before:

$ minikube addons enable dashboard
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x228 pc=0x102386bb8]

goroutine 1 [running]:
k8s.io/minikube/cmd/minikube/cmd/config.glob..func11(0x14000168f00?, {0x14000110eb0, 0x1, 0x102425f1c?})
        /Users/powellsteven/repo/minikube/cmd/minikube/cmd/config/enable.go:47 +0x198
github.com/spf13/cobra.(*Command).execute(0x1044f9920, {0x14000110e50, 0x1, 0x1})
        /Users/powellsteven/go/pkg/mod/github.com/spf13/cobra@v1.7.0/command.go:944 +0x640
github.com/spf13/cobra.(*Command).ExecuteC(0x1044f4b80)
        /Users/powellsteven/go/pkg/mod/github.com/spf13/cobra@v1.7.0/command.go:1068 +0x320
github.com/spf13/cobra.(*Command).Execute(...)
        /Users/powellsteven/go/pkg/mod/github.com/spf13/cobra@v1.7.0/command.go:992
k8s.io/minikube/cmd/minikube/cmd.Execute()
        /Users/powellsteven/repo/minikube/cmd/minikube/cmd/root.go:174 +0x54c
main.main()
        /Users/powellsteven/repo/minikube/cmd/minikube/main.go:95 +0x258

After:

$ minikube addons enable dashboard
🤷  Profile "minikube" not found. Run "minikube profile list" to view all profiles.
👉  To start a cluster, run: "minikube start"

Disabling Addon

Before:

$ minikube addons disable dashboard

❌  Exiting due to MK_ADDON_DISABLE_PAUSED: disable failed: loading profile: cluster "minikube" does not exist

╭─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│                                                                                                                         │
│    😿  If the above advice does not help, please let us know:                                                           │
│    👉  https://github.com/kubernetes/minikube/issues/new/choose                                                         │
│                                                                                                                         │
│    Please run `minikube logs --file=logs.txt` and attach logs.txt to the GitHub issue.                                  │
│    Please also attach the following file to the GitHub issue:                                                           │
│    - /var/folders/9l/6wpxv6wd1b901m1146r579wc00rqw3/T/minikube_addons_42a1f787df8d0157be2dce836a5f91db2b8ab26d_0.log    │
│                                                                                                                         │
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

After:

$ minikube addons disable dashboard
🤷  Profile "minikube" not found. Run "minikube profile list" to view all profiles.
👉  To start a cluster, run: "minikube start"

[medyagh]

/ok-to-test

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: medyagh, spowelljr

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• OWNERS [medyagh,spowelljr]

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[minikube-pr-bot]

kvm2 driver with docker runtime
error collecting results for kvm2 driver: timing run 0 with minikube: timing cmd: [out/minikube start --driver=kvm2 --container-runtime=docker]: waiting for minikube: exit status 90
docker driver with docker runtime
error downloading artifacts: artifact download start: exit status 81docker driver with containerd runtime
error downloading artifacts: artifact download start: exit status 81

[minikube-pr-bot]

These are the flake rates of all failed tests.

Environment	Failed Tests	Flake Rate (%)
Hyperkit_macOS	TestNetworkPlugins/group/custom-flannel/Start (gopogh)	4.39 (chart)

To see the flake rates of all tests by environment, click here.