The Git Hang and the Admin/Mod user Accs Oops Error Page Error

I want to paste this to preserve it so I can close a tab - untested code from the llm, presented here as a monkey patch to apply in the rails console to a running system, but also containing an llm-suggested fix for this fragility which causes the oops:

# Re-open the CurrentUserSerializer to override the broken method
class CurrentUserSerializer < ApplicationSerializer
  def has_new_upcoming_changes
    last_visited = object.custom_fields["last_visited_upcoming_changes_at"]
    
    # Extract string if cached as an array by the preloader
    last_visited = last_visited.first if last_visited.is_a?(Array)
    
    return false if last_visited.blank? && object.created_at < Discourse.site_creation_date + 1.hour
    cutoff = last_visited.present? ? Time.zone.parse(last_visited.to_s) : object.created_at
    UpcomingChangeEvent.added.not_backfilled.where("created_at > ?", cutoff).exists?
  end
end