HCL local referencing variable crash.log

crash.log

2020/03/17 19:19:13 [INFO] Packer version: 1.5.4 [go1.13.8 darwin amd64]
2020/03/17 19:19:13 Checking 'PACKER_CONFIG' for a config file path
2020/03/17 19:19:13 'PACKER_CONFIG' not set; checking the default config file path
2020/03/17 19:19:13 Attempting to open config file: /Users/robzr/.packerconfig
2020/03/17 19:19:13 [WARN] Config file doesn't exist: /Users/robzr/.packerconfig
2020/03/17 19:19:13 Setting cache directory: /Users/robzr/github/ss_homework/packer/packer_cache
2020/03/17 19:19:13 waiting for all plugin processes to complete...
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4a183d7]

goroutine 1 [running]:
github.com/hashicorp/packer/hcl2template.(*Variable).Value(0xc0002486e0, 0xc000204990, 0xc000614f20, 0x0, 0x0, 0xc0000b4800)
        /private/tmp/packer-20200215-62787-y95gm9/hcl2template/types.variables.go:64 +0x197
github.com/hashicorp/packer/hcl2template.Variables.Values(0xc000204990, 0xc000205290)
        /private/tmp/packer-20200215-62787-y95gm9/hcl2template/types.variables.go:73 +0xc3
github.com/hashicorp/packer/hcl2template.(*PackerConfig).EvalContext(0xc0001c6a80, 0xc000204ae0)
        /private/tmp/packer-20200215-62787-y95gm9/hcl2template/types.packer_config.go:39 +0x111
github.com/hashicorp/packer/hcl2template.(*Parser).getBuilds(0xc000615370, 0xc0001c6a80, 0x0, 0xc000204000, 0xc0001c6a80, 0x0, 0x0, 0x0)
        /private/tmp/packer-20200215-62787-y95gm9/hcl2template/types.packer_config.go:104 +0x1ab
github.com/hashicorp/packer/hcl2template.(*Parser).Parse(0xc000615370, 0x7ffeefbff57f, 0x1, 0xc0002040f0, 0xc0002c5d40, 0xc000615330, 0x40d95ed, 0x7ffeefbff57f, 0x1, 0x84c3200)
        /private/tmp/packer-20200215-62787-y95gm9/hcl2template/types.packer_config.go:167 +0xd1
github.com/hashicorp/packer/command.(*BuildCommand).GetBuildsFromHCL(0xc00020a240, 0x7ffeefbff57f, 0x1, 0x0, 0x0, 0xc0000b4800, 0x1)
        /private/tmp/packer-20200215-62787-y95gm9/command/build.go:107 +0x123
github.com/hashicorp/packer/command.(*BuildCommand).GetBuilds(0xc00020a240, 0x7ffeefbff57f, 0x1, 0x4, 0x0, 0x7fffffffffffffff, 0x0)
        /private/tmp/packer-20200215-62787-y95gm9/command/build.go:136 +0x543
github.com/hashicorp/packer/command.(*BuildCommand).RunContext(0xc00020a240, 0x84a7760, 0xc00010bc40, 0xc0000e6140, 0x4, 0x4, 0xc00010bc40)
        /private/tmp/packer-20200215-62787-y95gm9/command/build.go:185 +0xca
github.com/hashicorp/packer/command.(*BuildCommand).Run(0xc00020a240, 0xc0000e6140, 0x4, 0x4, 0x0)
        /private/tmp/packer-20200215-62787-y95gm9/command/build.go:55 +0x201
github.com/mitchellh/cli.(*CLI).Run(0xc00010e780, 0xc00010e780, 0x1, 0x1)
        /private/tmp/packer-20200215-62787-y95gm9/.brew_home/go/pkg/mod/github.com/mitchellh/cli@v1.0.0/cli.go:255 +0x1da
main.wrappedMain(0x0)
        /private/tmp/packer-20200215-62787-y95gm9/main.go:238 +0x853
main.realMain(0x0)
        /private/tmp/packer-20200215-62787-y95gm9/main.go:124 +0xbb
main.main()
        /private/tmp/packer-20200215-62787-y95gm9/main.go:34 +0x22