I suspect this may be actually a bug in the gerrit plugin. Specifically: https://github.com/jenkinsci/gerrit-trigger-plugin/blob/master/src/main/java/com/sonyericsson/hudson/plugins/gerrit/trigger/PluginImpl.java#L470-L490
Searching the extension lists for other plugin classes before InitMilestone.EXTENSIONS_AUGMENTED will cause the world to blow up...
Doing things like starting a connection to the Gerrit server (which will need credentials...) is not what should happen in the confusingly named Plugin#start() method.
Moving this bug over to gerrit who actually own the issue.
As to why reverting "worked"... well I think you just changed the order that plugins get loaded into the Guice container because of the version number change which had an ever so subtle effect on the plugin dependency graph