panic: interface conversion: interface {} is nil, not string
goroutine 1 [running]:
github.com/garethr/kubeval/kubeval.validateResource(0xc420088d80, 0x5, 0x205, 0x7ffc6055df6f, 0x11, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/go/src/github.com/garethr/kubeval/kubeval/kubeval.go:131 +0x9fd
github.com/garethr/kubeval/kubeval.Validate(0xc420088d80, 0x5, 0x205, 0x7ffc6055df6f, 0x11, 0x0, 0x0, 0x0, 0xc4200cb900, 0x0)
/go/src/github.com/garethr/kubeval/kubeval/kubeval.go:174 +0x1e9
github.com/garethr/kubeval/cmd.glob..func1(0xa94160, 0xc420112e40, 0x1, 0x1)
/go/src/github.com/garethr/kubeval/cmd/root.go:67 +0x1f6
github.com/garethr/kubeval/vendor/github.com/spf13/cobra.(*Command).execute(0xa94160, 0xc42000c110, 0x1, 0x1, 0xa94160, 0xc42000c110)
/go/src/github.com/garethr/kubeval/vendor/github.com/spf13/cobra/command.go:654 +0x299
github.com/garethr/kubeval/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xa94160, 0xc4200cb680, 0x0, 0x0)
/go/src/github.com/garethr/kubeval/vendor/github.com/spf13/cobra/command.go:729 +0x339
github.com/garethr/kubeval/vendor/github.com/spf13/cobra.(*Command).Execute(0xa94160, 0x0, 0x6e)
/go/src/github.com/garethr/kubeval/vendor/github.com/spf13/cobra/command.go:688 +0x2b
github.com/garethr/kubeval/cmd.Execute()
/go/src/github.com/garethr/kubeval/cmd/root.go:99 +0x31
main.main()
/go/src/github.com/garethr/kubeval/main.go:6 +0x20