Fix users seeds

Author: tb

db/seeds.rb

@@ -13,6 +13,10 @@
 end
 
 25.times do |n|
-  u = User.create!(email: "user#{n}@example.com", password: 'Secret123', confirmed_at: Time.now)
-  u.add_role n == 0 ? :admin : :user
+  User.create!(
+    email: "user#{n}@example.com",
+    password: 'Secret123',
+    confirmed_at: Time.now,
+    tokens: nil
+  ).add_role n == 0 ? :admin : :user
 end