panic when not specifying a region

[markpeek]

$ gghelper creategroup -name test
CreateCore error: MissingRegion: could not find region configuration
Created core 'test'
CreateCoreDefinition error: MissingRegion: could not find region configuration
Error: MissingRegion: could not find region configuration
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x70e7ee]

goroutine 1 [running]:
github.com/cloudtools/gghelper.(*GreengrassSession).GetConfigArchive(0xc420150000, 0x0)
/Users/mark/go/src/github.com/cloudtools/gghelper/archive.go:37 +0x19e
main.CreateGroup(0xc42000e0a0, 0x2, 0x2)
/Users/mark/go/src/github.com/cloudtools/gghelper/cmd/gghelper/group.go:36 +0x2cc
main.main()
/Users/mark/go/src/github.com/cloudtools/gghelper/cmd/gghelper/gghelper.go:40 +0x637