github input panics when repo has no language

[russorat]

Relevant telegraf.conf:

[[inputs.github]]
  ## List of repositories to monitor
  repositories = [
        "influxdata/community"
  ]

  ## Github API access token.  Unauthenticated requests are limited to 60 per hour.
  access_token = "<SOMETHING>"

  ## Timeout for HTTP requests.
  # http_timeout = "5s"

System info:

master branch, mac os

Steps to reproduce:

1. Start Telegraf with this config, telegraf panics

Expected behavior:

Telegraf should not panic

Actual behavior:

Telegraf panics

Additional info:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x4b6ddca]

goroutine 5820 [running]:
github.com/influxdata/telegraf/plugins/inputs/github.getTags(...)
	/Users/rsavage/go/src/github.com/influxdata/telegraf/plugins/inputs/github/github.go:163
github.com/influxdata/telegraf/plugins/inputs/github.(*GitHub).Gather.func1(0xc0013a7aa0, 0xc000160380, 0x669cee0, 0xc0000dc008, 0xc00015a561, 0x14, 0x66b8420, 0xc00019c100)
	/Users/rsavage/go/src/github.com/influxdata/telegraf/plugins/inputs/github/github.go:130 +0x32a
created by github.com/influxdata/telegraf/plugins/inputs/github.(*GitHub).Gather
	/Users/rsavage/go/src/github.com/influxdata/telegraf/plugins/inputs/github/github.go:106 +0x136

[russorat]

i think this also happens if you hit the API limits from github.

[glinton]

i think this also happens if you hit the API limits from github.

Is it a similar panic or just error?