$ rake db:migrate
rake aborted!
undefined method `accept' for nil:NilClass

Tasks: TOP => db:migrate
(See full trace by running task with --trace)

activemodel (3.2.8)
activerecord (3.2.8)
activerecord-mysql2-adapter (0.0.3)
builder (3.1.3, 3.0.3)
bundler (1.2.1)
mysql2 (0.3.2)

rails (3.2.8)
rails_apps_composer (2.2.10)
railties (3.2.8)
rake (0.9.2.2)
rdoc (3.12)
sqlite3 (1.3.6)
therubyracer (0.10.2)
thor (0.16.0)
tilt (1.3.3)
treetop (1.4.10)
twitter-bootstrap-rails (2.1.3)
tzinfo (0.3.33)
uglifier (1.3.0)

development:
  adapter: mysql2
  database: tripwall
  username: root
  password: pass
  host: localhost
  pool: 5
  timeout: 5000

NoMethodError (undefined method `accept' for nil:NilClass):
app/controllers/posts_controller.rb:5:in `index'