UserStore handles GitHub remotes that no longer exist

[smashwilson]

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Description of the Change

Break from the user accumulation loop in UserStore when the GraphQL response includes a null Repository.

Alternate Designs

When you have no GitHub remotes at all, we currently fall back to your local git history to populate the UserStore. Given that we now have the possibility that your GitHub remote could no longer exist, it may make sense to fall back to that in the instance that no valid GitHub remotes are found any more. I opted not to go that route in this take to keep the change small and minimize risk.

Benefits

A stacktrace on package activation no longer occurs.

Possible Drawbacks

If you delete all GitHub repositories referenced by your git remotes - or add a bunch of fake ones - your UserStore will stay empty.

Applicable Issues

Fixes #1867.

Metrics

N/A

Tests

I've added a unit test to capture the null-Repository case to verify the fix.

Documentation

N/A

Release Notes

• The GitHub package no longer logs an exception when a remote has been deleted on github.com.

User Experience Research (Optional)

N/A

[codecov]

Codecov Report

Merging #1869 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1869   +/-   ##
=======================================
  Coverage   91.14%   91.14%           
=======================================
  Files         196      196           
  Lines       10745    10745           
  Branches     1575     1575           
=======================================
  Hits         9794     9794           
  Misses        951      951

Impacted Files	Coverage Δ
lib/models/user-store.js	99.19% <100%> (+0.8%)	⬆️
lib/models/operation-states.js	89.58% <0%> (-2.09%)	⬇️

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[annthurium]

Thanks @smashwilson for fixing this!