Local customizations broke site on upgrade, how to disable?

None.

Reading this: https://meta.discourse.org/t/deprecating-objectcontroller/28385?u=jesselperry

I think I have a customization that gets the current logged in user name. Could that be causing this error? The this.get('name') in the post made me think of that customization.

Any way to disable that customization, even though I can’t get into /admin?