RFR: 2091: CheckRun fails with NPE if github fullName is null

[Zhao Song]

If a user doesn't set name in the GitHub profile, when the bot is trying to get the full name of the user, the bot would get `null` and in some cases, it will trigger NPE.

To solve this problem, I think if the user doesn't set name, then the bot should use his username instead.

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Commit messages:
 - SKARA-2091

Changes: https://git.openjdk.org/skara/pull/1582/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1582&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2091
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/skara/pull/1582.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1582/head:pull/1582

PR: https://git.openjdk.org/skara/pull/1582