Rails/Mailer - NoMethodError after sending email - ruby-on-rails

Question

I'm fairly new to Rails, so this will likely end up being something obvious; however I've just spent the better part of a day pulling my hair out over this issue.
I have a rails app which I've been working on for awhile, however I only started implementing mailers today. I followed the Rails ActionMailer tutorial here: http://guides.rubyonrails.org/v3.0.3/action_mailer_basics.html and the mailer works fine in a new example app. However, when I repeated those steps verbatim in my existing rails app (running in Development environment) I receive the below error. It creates the entry in the DB, correctly sends both the plain text & HTML emails and THEN generates the error. All I'm trying to do here is send a welcome email upon the creation of a new account, but I'm getting the same error when I try to send any email from any controller.
The specific error I'm seeing after it sends the welcome email is:
Completed 500 Internal Server Error in 280ms
NoMethodError (undefined method `error' for true:TrueClass):
app/controllers/musers_controller.rb:52:in `block in create'
app/controllers/musers_controller.rb:50:in `create'
Note that to not mess up my existing User table, I created a temporary scaffold & mailer called Muser which I plan on deleting once I'm confident this will work correctly on my user table.
Code
Error in log:
Started POST "/musers" for 127.0.0.1 at 2013-07-10 20:32:34 -0400
Processing by MusersController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"OuoEmsjkAVBHZwqPO5b/O4eKw6iZBaLP6vUT6f9WCOI=", "muser"=>{"name"=>"New User", "email"=>"User#email.com"}, "commit"=>"Create"}
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 1]]
(0.1ms) begin transaction
SQL (0.6ms) INSERT INTO "musers" ("created_at", "email", "name", "updated_at") VALUES (?, ?, ?, ?) [["created_at", Thu, 11 Jul 2013 00:32:34 UTC +00:00], ["email", "User#email.com"], ["name", "New User"], ["updated_at", Thu, 11 Jul 2013 00:32:34 UTC +00:00]]
(1.7ms) commit transaction
Rendered muser_mailer/registration_confirmation.html.erb (0.1ms)
Rendered muser_mailer/registration_confirmation.text.erb (0.0ms)
Completed 500 Internal Server Error in 280ms
NoMethodError (undefined method `error' for true:TrueClass):
app/controllers/musers_controller.rb:52:in `block in create'
app/controllers/musers_controller.rb:50:in `create'
Rendered /usr/local/rvm/gems/ruby-1.9.3-p194/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/_trace.erb (2.6ms)
Rendered /usr/local/rvm/gems/ruby-1.9.3-p194/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (2.5ms)
Rendered /usr/local/rvm/gems/ruby-1.9.3-p194/gems/actionpack-3.2.8/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (15.3ms)
--I should note that lines 50 & 52 of the musers_controller (where this error is being generated) correspond to the 'respond_to do' & 'MuserMailer.... .deliver' lines in the controller code below.--
The controller action:
# POST /musers
# POST /musers.json
def create
#muser = Muser.new(params[:muser])
respond_to do |format|
if #muser.save
MuserMailer.registration_confirmation(#muser).deliver
format.html { redirect_to #muser, notice: 'Muser was successfully created.' }
format.json { render json: #muser, status: :created, location: #muser }
else
format.html { render action: "new" }
format.json { render json: #muser.errors, status: :unprocessable_entity }
end
end
end
Mailer:
class MuserMailer < ActionMailer::Base
default from: "EmailAddress#Inter.net"
def registration_confirmation(muser)
#muser = muser
mail(:to => muser.email, :subject => "Registered")
end
end
I don't think that the issue is with my smtp, mail setup, or variables since it does actually add to the DB & send the emails correctly. If I comment out the line in the controller which calls the mail action the error disappears, so I don't think the problem is with my muser routes. This undefined method 'error' for true:TrueClass is driving me nuts. I did recently install Devise on my Users table, so I don't know if that could be causing the issue?
For lack of a better term, it feels like the issue is with how Rails wants to route after sending the emails; as if I need to put a Return or specify a route at the end of my mailer action telling the server to head back to the controller action. In other words, I'm lost!
Update
Below are the two mailer view files I'm using.
registration_confirmation.html.erb
<h3><%= #muser.name %>! You sweet sweet fool!</h3>
<p>Thank you for registering!</p>
registration_confirmation.text.erb
Thank you for registering!
Update 2
Here's my model for Muser:
class Muser < ActiveRecord::Base
attr_accessible :email, :name
end

Answer 1

I solved this issue - there was the errant line config.action_mailer.logger = true in my config/environments/development.rb file that was causing the issues. Once removed everything worked perfectly.