Invalid memory address or nil pointer dereference when linting

[AnesBenmerzoug]

Is this a BUG REPORT or FEATURE REQUEST?:

Bug Report

What happened:

When running the lint command on any template I get the following error:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0xf67bf5]

goroutine 1 [running]:
github.com/argoproj/argo/pkg/client/clientset/versioned.(*Clientset).ArgoprojV1alpha1(0x0, 0xc00041daa0, 0x14fa987)
	/home/koutetsu/go/src/github.com/argoproj/argo/pkg/client/clientset/versioned/clientset.go:26 +0x5
github.com/argoproj/argo/workflow/validate.ValidateWorkflow(0x1683aa0, 0x0, 0x14f4988, 0x7, 0xc000585180, 0x1, 0x0, 0x0, 0x0, 0x199)
	/home/koutetsu/go/src/github.com/argoproj/argo/workflow/validate/validate.go:90 +0x27e
github.com/argoproj/argo/workflow/validate.LintWorkflowFile(0x1683aa0, 0x0, 0x14f4988, 0x7, 0x7ffe51e58077, 0x19, 0x1, 0x1, 0x11)
	/home/koutetsu/go/src/github.com/argoproj/argo/workflow/validate/lint.go:65 +0x4cc
github.com/argoproj/argo/cmd/argo/commands.NewLintCommand.func1(0xc00028a780, 0xc0001e5080, 0x1, 0x1)
	/home/koutetsu/go/src/github.com/argoproj/argo/cmd/argo/commands/lint.go:50 +0x283
github.com/argoproj/argo/vendor/github.com/spf13/cobra.(*Command).execute(0xc00028a780, 0xc0001e5030, 0x1, 0x1, 0xc00028a780, 0xc0001e5030)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:766 +0x2cc
github.com/argoproj/argo/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xc000113180, 0xc00028b900, 0xc00028b680, 0xc00028aa00)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:852 +0x2fd
github.com/argoproj/argo/vendor/github.com/spf13/cobra.(*Command).Execute(0xc000113180, 0x0, 0xc000284d80)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:800 +0x2b
main.main()
	/home/koutetsu/go/src/github.com/argoproj/argo/cmd/argo/main.go:17 +0x27
roj/argo/vendor/github.com/spf13/cobra.(*Command).execute(0xc00028a780, 0xc0001e5030, 0x1, 0x1, 0xc00028a780, 0xc0001e5030)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:766 +0x2cc
github.com/argoproj/argo/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xc000113180, 0xc00028b900, 0xc00028b680, 0xc00028aa00)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:852 +0x2fd
github.com/argoproj/argo/vendor/github.com/spf13/cobra.(*Command).Execute(0xc000113180, 0x0, 0xc000284d80)
	/home/koutetsu/go/src/github.com/argoproj/argo/vendor/github.com/spf13/cobra/command.go:800 +0x2b
main.main()
	/home/koutetsu/go/src/github.com/argoproj/argo/cmd/argo/main.go:17 +0x27

What you expected to happen:

Before this bug, the cli would print the following:

Workflow Validated

How to reproduce it (as minimally and precisely as possible):

On the current master branch, simply build the cli and run:

./dist/argo lint examples/hello-world.yaml

Linting works on commit 4864c32ffa40861c5ca066f67615da6d52eaa8b5

After running git bisect I found that the bug was introduced in commit 0246d184add04e44f77ffbe00e796b3adaf535d2

Anything else we need to know?:

Environment:

• Argo version:

$ argo version
argo: v2.4.0+5331fc0.dirty
  BuildDate: 2019-08-12T18:44:43Z
  GitCommit: 5331fc02e257266a4a5887dfe6277e5a0b42e7fc
  GitTreeState: dirty
  GoVersion: go1.11.12
  Compiler: gc
  Platform: linux/amd64

• Kubernetes version :

$ kubectl version -o yaml
clientVersion:
  buildDate: "2019-08-05T17:09:13Z"
  compiler: gc
  gitCommit: f6278300bebbb750328ac16ee6dd3aa7d3549568
  gitTreeState: clean
  gitVersion: v1.15.2
  goVersion: go1.12.7
  major: "1"
  minor: "15"
  platform: linux/amd64
serverVersion:
  buildDate: "2019-06-19T16:32:14Z"
  compiler: gc
  gitCommit: e8462b5b5dc2584fdcd18e6bcfe9f1e4d970a529
  gitTreeState: clean
  gitVersion: v1.15.0
  goVersion: go1.12.5
  major: "1"
  minor: "15"
  platform: linux/amd64