Panic when uploading big artifacts bundle to gitlab

I had a panic when uploading big artifacts bundle to gitlab. It recovered from the panic and subsequent builds are running normaly, so no big issue. But as a developer, I would love to know where to improve my errorhandling.

So here is the backtrace:

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x611d87]

goroutine 1 [running]:
panic(0xa7fa00, 0xc8200140d0)
	/usr/local/go/src/runtime/panic.go:481 +0x3e6
main.main.func1()
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/main.go:46 +0x77
panic(0xa7fa00, 0xc8200140d0)
	/usr/local/go/src/runtime/panic.go:443 +0x4e9
gitlab.com/gitlab-org/gitlab-ci-multi-runner/network.(*GitLabClient).UploadRawArtifacts(0xc82002c090, 0xbeb, 0x7ffe9b8389b7, 0x14, 0x7ffe9b838991, 0x1d, 0xc820016016, 0x51, 0x7fd3534ec090, 0xc82002c1e0, ...)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/network/gitlab.go:323 +0x1607
gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers.(*ArtifactsUploaderCommand).createAndUpload(0xc8200c4210, 0x4b0300, 0x0, 0x0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers/artifacts_uploader.go:42 +0x34c
gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers.(*ArtifactsUploaderCommand).(gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers.createAndUpload)-fm(0x0, 0x0, 0x0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers/artifacts_uploader.go:73 +0x2e
gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers.(*retryHelper).doRetry(0xc8200c4280, 0xc8204c14e0, 0x0, 0x0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers/retry_helper.go:14 +0x38
gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers.(*ArtifactsUploaderCommand).Execute(0xc8200c4210, 0xc8200d82d0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/commands/helpers/artifacts_uploader.go:73 +0x27c
gitlab.com/gitlab-org/gitlab-ci-multi-runner/common.(Commander).Execute-fm(0xc8200d82d0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/common/command.go:24 +0x3c
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli.Command.Run(0xbc1670, 0x12, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc100a0, 0x2c, 0x0, ...)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli/command.go:127 +0x1055
gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli.(*App).Run(0xc820090c00, 0xc82000a0e0, 0xe, 0xe, 0x0, 0x0)
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/vendor/github.com/codegangsta/cli/app.go:159 +0xc34
main.main()
	/go/src/gitlab.com/gitlab-org/gitlab-ci-multi-runner/main.go:76 +0x2c2

ERROR: Build failed: exit status 1

Version and Environment:

Version:      1.3.2
Git revision: 0323456
Git branch:   stable-1-3
GO version:   go1.6.2
Built:        Tue, 28 Jun 2016 14:03:09 +0000
OS/Arch:      linux/amd64