I am having a compatability issue with the plugin. Source maps of old save files will not load when the plugin is enabled. New game files run with no problem. I disabled Visustella Main Menu core but that did not help.
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Setting it to 0 does disable it, but the problem is the code is still checking for it being there so whether enabled or not you'll still have this issue. It's because the object is created on game start, so obviously it doesn't exist in your save.
I'll update the plugin to create the object if it doesn't exist when it's needed. Should have a new version up soon, thanks for the report!