Try to fix wrong try usage

`Object#try` checks "whether receiver is nil or not". It doesn't rescue
any exceptions raised in method call.

    > User.new(name: "admin", password_digest: "invalid-hash").authenticate("X")
    BCrypt::Errors::InvalidHash: invalid hash
            from /var/lib/gems/2.1.0/gems/bcrypt-3.1.7/lib/bcrypt/password.rb:60:in `initialize'
            ...

app/controllers/application_controller.rb

@@ -16,8 +16,7 @@ class ApplicationController < ActionController::Base
 
   def current_user
     return unless session[:succeed_password]
-    # NOTE: if hashed password is invalid or broken, .authenticate would raise error. Using `try` is avoid that situation
-    @current_user ||= User.new(name: "admin").try(:authenticate, session[:succeed_password])
+    @current_user ||= User.new(name: "admin").authenticate(session[:succeed_password])
   end
 
   def login_required

app/models/user.rb

@@ -19,6 +19,12 @@ class User
   validates :password, length: { minimum: 8 }
   validate :valid_current_password
 
+  def authenticate(unencrypted_password)
+    super
+  rescue BCrypt::Errors::InvalidHash
+    false
+  end
+
   def password_digest
     @password_digest ||
       begin