Remove roles when block or delete users

After a user assigned as a budget admin deletes their account or gets blocked by
a moderator, the application throws an exception while loading the admin
investment index page.

As an erased user is not really deleted and neither its associated roles, the
application was failing when trying to sort and administration without a
username. In this case, the application was throwing an `ArgumentError:
comparison of NilClass with String failed` exception.

As a blocked user is not deleted or its roles, the application failed when trying
to access the user name through the delegation in the Administrator. In this
case, the application was throwing a `NoMethodError: undefined method `name' for
nil:NilClass` exception.

app/models/user.rb

@@ -230,6 +230,7 @@ class User < ApplicationRecord
     Proposal.hide_all proposal_ids
     Budget::Investment.hide_all budget_investment_ids
     ProposalNotification.hide_all ProposalNotification.where(author_id: id).ids
+    remove_roles
   end
 
   def full_restore
@@ -263,12 +264,21 @@ class User < ApplicationRecord
       unconfirmed_phone: nil
     )
     identities.destroy_all
+    remove_roles
   end
 
   def erased?
     erased_at.present?
   end
 
+  def remove_roles
+    administrator&.destroy!
+    valuator&.destroy!
+    moderator&.destroy!
+    manager&.destroy!
+    sdg_manager&.destroy!
+  end
+
   def take_votes_if_erased_document(document_number, document_type)
     erased_user = User.erased.find_by(document_number: document_number,
                                       document_type: document_type)