Panic with ONBUILD ARG and ONBUILD ENV

[tpansino]

$> dockerfmt version
dockerfmt 0.3.7

$> cat Dockerfile
FROM ubuntu:latest

ONBUILD ARG MY_ARG

$> dockerfmt --newline --check Dockerfile
panic: runtime error: index out of range [1] with length 1

goroutine 1 [running]:
github.com/reteps/dockerfmt/lib.formatBasic(0xc00012a680, 0xc00011a420)
        /github/workspace/lib/format.go:418 +0xeb
github.com/reteps/dockerfmt/lib.FormatNode(0xc00012a680, 0xc00011a420)
        /github/workspace/lib/format.go:69 +0x51f
github.com/reteps/dockerfmt/lib.FormatOnBuild(0xc00012a600, 0xc000197910?)
        /github/workspace/lib/format.go:116 +0x3e
github.com/reteps/dockerfmt/lib.FormatNode(0xc00012a600, 0xc00011a420)
        /github/workspace/lib/format.go:69 +0x51f
github.com/reteps/dockerfmt/lib.(*ParseState).processNode(0xc000197a40, 0xc00012a600)
        /github/workspace/lib/format.go:94 +0xf9
github.com/reteps/dockerfmt/lib.(*ParseState).processNode(0xc000197a40, 0xc00012a540)
        /github/workspace/lib/format.go:103 +0x18b
github.com/reteps/dockerfmt/lib.FormatFileLines({0xc000127110, 0x3, 0x3}, 0xc00011a420)
        /github/workspace/lib/format.go:139 +0x246
github.com/reteps/dockerfmt/cmd.processInput({0x7fff3377c7ed, 0xa}, {0xc000190000?, 0x0?, 0x0?}, 0xc00011a420)
        /github/workspace/cmd/root.go:81 +0xc6
github.com/reteps/dockerfmt/cmd.Run(0x87c320, {0xc000127080, 0x1, 0x68632e?})
        /github/workspace/cmd/root.go:65 +0x1d1
github.com/spf13/cobra.(*Command).execute(0x87c320, {0xc00012a090, 0x3, 0x3})
        /go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1019 +0xa7b
github.com/spf13/cobra.(*Command).ExecuteC(0x87c320)
        /go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1148 +0x40c
github.com/spf13/cobra.(*Command).Execute(...)
        /go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1071
github.com/reteps/dockerfmt/cmd.Execute()
        /github/workspace/cmd/root.go:112 +0x1a
main.main()
        /github/workspace/main.go:8 +0xf

This also occurs if you replace the ONBUILD ARG with ONBUILD ENV.

[reteps]

Closed by https://github.com/reteps/dockerfmt/releases/tag/v0.3.8