Rake task for merging users

@gerhard Any chance that merging users on a site with the Discourse Topic Voting Plugin plugin will prevent one of those users from logging in with the following error and log message?

The software powering this discussion forum encountered an unexpected problem. We apologize for the inconvenience.

Disabling the plugin solves the problem, but I like the plugin, so ideas on how I could fix it are very welcome!

The line in question is at https://github.com/discourse/discourse-voting/blob/master/plugin.rb#L112 and I think I’ve fixed it at https://github.com/discourse/discourse-voting/pull/33.