Delete a user with rails - fails

Technical assistance
5

It was a testuser, therefore he could be an agent/admin/customer.

I am getting this error.

irb(main):001:0> Ticket.find_by(customer_id:13).pluck(:id)
Traceback (most recent call last):
        1: from (irb):1
NoMethodError (undefined method `pluck' for nil:NilClass)
irb(main):002:0> Ticket.find_by(owner_id:13).pluck(:id)
Traceback (most recent call last):
        1: from (irb):2
NoMethodError (undefined method `pluck' for nil:NilClass)
irb(main):003:0> Ticket.find_by(created_by_id:13).pluck(:id)
Traceback (most recent call last):
        1: from (irb):3
NoMethodError (undefined method `pluck' for #<Ticket:0x000055ecd1cda3e8>)
irb(main):004:0> Ticket.find_by(updated_by_id:13).pluck(:id)
Traceback (most recent call last):
        1: from (irb):4
NoMethodError (undefined method `pluck' for #<Ticket:0x000055ecd1c1a110>)
irb(main):005:0>

Did i something wrong?

Thank you for your help :sunglasses: