private method `update_without_password' called for nil:NilClass

I am following this tutorial on cancancan authentication, and specifically wanting admins to update users without needing a password. I've also seen this suggestion, but am unsure how to adapt it into my own code. When I click update, it says 'NoMethodError in UsersController#update' private method `update_without_password' called for nil:NilClass

My app returns all the user's params, so I don't understand what's happening here. Still very new to rails - let me know if you need any further information. Thank you in advance!

USERS CONTROLLER

class UsersController < ApplicationController
before_filter :authenticate_user!



 def update
  if user_params[:password].blank?
    user_params.delete(:password)
    user_params.delete(:password_confirmation)
  end


  successfully_updated = if needs_password?(@user, user_params)
                           @user.update(user_params)
                         else
                           @user.update_without_password(user_params)
                         end
 respond_to do |format|
    if successfully_updated
      format.html { redirect_to @user, notice: 'User was successfully updated.' }
      format.json { head :no_content }
    else
      format.html { render action: 'edit' }
      format.json { render json: @user.errors, status: :unprocessable_entity }
    end
  end


  rescue ActiveRecord::RecordNotFound
    respond_to_not_found(:js, :xml, :html)
  end


private
def needs_password?(user, params)
  params[:password].present?
end

def update_without_password(user_params)
  user.update_without_password(user_params)
end



def user_params
        params.require(:user).permit(:first_name, :last_name, :email, :password, :password_confirmation, :name, :role_id, :accepted)
end

EDIT FORM

<h3><%= @user == @current_user ? "Your Account Settings" : "Edit User" %></h3>

<%= form_for(@user, :html => { :method => :put }) do |f| %>
 <p><%= f.label :first_name %></p>
 <p><%= f.text_field :first_name %></p>

 <p><%= f.label :last_name %></p>
 <p><%= f.text_field :last_name %></p>

 <p><%= f.label :email %></p>
 <p><%= f.text_field :email %></p>
  <% if can? :read, Role %>
 <%= collection_select(:user, :role_id, Role.all, :id, :name, {prompt: true}) %>
  <% end %>
 <p><%= f.submit "Update" %></p>
<% end %>

What am I missing here? Please let me know if should provide anything else. Thanks!!