Add and clean-up null-checks.

Change-Id: I4af4c6c3342f19cfc93a27c42ff150818c812e2b
Merge branch 'master' into nullchecks
Restore English as default language in server config page.

Add EnablePluginMessages back.

Change-Id: If791839e2982837c14578aeb08eadc7c5921e8c4
Merge pull request #85 from mathieu-wang/nullchecks

Add and clean-up null-checks.
Merge pull request #86 from mathieu-wang/fix-gerritserver-language

Restore English as default language in server config page.
More null checks
Handle concurrent Gerrit queries and manual triggers with different servers and users.

Remove member variable containing server name info.
Get the information from the current HTTPSession instead.

Change-Id: I32b5acddf95b221a1cdeb552174c326bbd902b0b
Merge pull request #87 from mathieu-wang/manual-trigger

Handle concurrent Gerrit queries and manual triggers with different serv...