login is shown on GitHub tab when internet is disabled.

[annthurium]

Description

When wifi is disabled, Atom GitHub tab asks you to log in. It would be better to show an error message saying you have no connectivity.

Steps to Reproduce

1. disable your wifi
2. open a new atom window
3. open the github tab

Expected behavior:

I'd see some kind of message that says "your internet is down" or whatever

Actual behavior:

The "login" button shows up instead.

Reproduces how often:

100% of the time

Versions

Atom : 1.30.0-dev-a62462f66
Electron: 2.0.3
Chrome : 61.0.3163.100
Node : 8.9.3

Additional Information