Aplicativo Reflorestando

Log dos sistema:

Started POST "/subact/413/comments" for 127.0.0.1 at 2016-03-17 13:19:43 +0100
Processing by CommentsController#create as JS
Parameters: {"utf8"=>"?", "comment"=>{"comment"=>""}, "button"=>"", "subact_id"=>"413"}
Subact Load (0.3ms) SELECT subacts.* FROM subacts WHERE subacts.id = 413 LIMIT 1
Act Load (0.2ms) SELECT acts.* FROM acts WHERE acts.id = 148 ORDER BY acts.id ASC LIMIT 1
Area Load (0.2ms) SELECT areas.* FROM areas WHERE areas.id = 162 ORDER BY areas.id ASC LIMIT 1
Land Load (0.2ms) SELECT lands.* FROM lands WHERE lands.id = 54 ORDER BY lands.id ASC LIMIT 1
User Load (0.2ms) SELECT users.* FROM users WHERE users.id = 1 ORDER BY users.id ASC LIMIT 1
Organization Load (0.2ms) SELECT organizations.* FROM organizations WHERE organizations.id = 1 ORDER BY organizations.id ASC LIMIT 1
Completed 500 Internal Server Error in 8ms

NoMethodError (undefined method []' for nil:NilClass): app/controllers/comments_controller.rb:8:in create'