Good morning. I'm sorry you've run into this problem, but I was able to identify and fix the issue very quickly this morning.
The problem was that I'd aliased a window that only exists if you're using the VisuStella ElementsStatusCore plugin. Since I'd aliased the window without checking if that plugin was imported first, if you're not using that plugin, this error comes up on load. I wrapped the alias in an if check to make sure the plugin was imported before it aliases the function from it, so that won't happen anymore.
Redownload the plugin from your library to get the new version.
Also, keep in mind this plugin requires the VisuStella BattleCore plugin to work. So if you're not using it either, you're going to get other problems that I won't be able to fix until I release a version of the plugin that doesn't need it. I only bring this up because most people who are using the VS_BattleCore plugin are also using the ElementsStatusCore plugin as well, and that wasn't the case for you.
-Ramza