And now I saw that hookedowinter started that topic which has pretty much the same question I asked before, with no answer so far. So I left my message here because I’d like to be notified of possible solutions.
The same thing happened with me, and after changing some codes in some php files the problem seems to be fixed. I hope that a new version of the plugin will be available so we can just update it and all files will be fixed at once.
Despite the error, looks like the plugin works normally.