Error when I run specs: First argument in form cannot contain nil or be empty

_experience_form.html.erb

<% if current_user?(@user) %>
	<%= render 'shared/error_messages', object: f.object %>
	<div class="title-area"> 
		<%= f.text_field :title, placeholder: "Enter title..." %>
	</div>
	<div class="text-area">
		<%= f.text_area :content, placeholder: "Compose new post..." %>
	</div>
		<%= f.submit "Post", class: "small-button", id: "post" %>
<% end %>

experiences_controller.rb

class ExperiencesController < ApplicationController

	before_action :signed_in_user, only: [:index, :create, :destroy]

	def index
		@experiences = Experience.paginate(page: params[:page], per_page: 10)
	end

  def show
    @experience = Experience.find(params[:id])
  end

  def create 
    @experience = current_user.experiences.build(experience_params)
    if @experience.save
      flash[:success] = "Post created!"
      redirect_to @experience
    else
      flash.now[:error] = "Couldn't post!"
      redirect_to current_user
    end
  end

  def destroy
    Experience.find(params[:id]).destroy
    flash[:success] = "Successfully deleted!"
    redirect_to current_user
  end

	private

	def experience_params
		params.require(:experience).permit(:content, :title)
	end 

	def signed_in_user
    unless signed_in?
      store_location
      redirect_to signin_url, notice: "Please sign in."  #flash[:notice]
    end
  end

end 

sessions_helper.rb

module SessionsHelper

	#chap 8.19

	def sign_in(user)
		remember_token = User.new_remember_token
		cookies.permanent[:remember_token] = remember_token
		user.update_attribute(:remember_token, User.digest(remember_token))
		self.current_user = user
	end 

	def signed_in?
		!current_user.nil?
	end 

	def current_user=(user)
		@current_user = user
	end 

	def current_user
		remember_token = User.digest(cookies[:remember_token])
		@current_user ||= User.find_by(remember_token: remember_token)
	end 

	def current_user?(user)
		user == current_user
	end

	def signed_in_user
    unless signed_in?
      store_location
      redirect_to signin_url, notice: "Please sign in."  #flash[:notice]
    end
  end

	def sign_out
		current_user.update_attribute(:remember_token, User.digest(User.new_remember_token))
		cookies.delete(:remember_token)
		self.current_user = nil
	end

	def redirect_back_or(default)
		redirect_to(session[:return_to] || default)
		session.delete(:return_to)
	end

	def store_location
		session[:return_to] = request.url if request.get?
	end 
end

show-user.html.erb

<% provide(:title, @user.name) %>
<div class="wrapper">
	<div class="left">
		<div id="username"><h1><%= link_to @user.name.upcase, @user %></h1></div>
		<div id="sidebar">
			<ul>
				<% if signed_in? && current_user?(@user) %>
				<li><%= link_to 'Settings', edit_user_path(@user, current_user), class: "small-button" %></li> 
				<li> <%= link_to 'Browse', '#', class: "small-button" %> </li>
				<li> <%= link_to  'Sign out', signout_path, method: 'delete', class: "small-button" %></li>
				<% else %>
				<li> <%=  link_to 'Follow', '#', class: "small-button" %> </li>
				<% end %>
			</ul>
		</div>
	</div>
	
	<div class="right">
		<div class="new-post"> 
			<%= form_for(@experience) do |f| %> 
				<%= render 'shared/experience_form', f: f %> 
			<% end %>
		</div>
		<div class="posts-wrapper">
		<% if @user.experiences.any? %>
		<%= will_paginate @experiences %>
			<ol>
				<%= render @experiences %>
			</ol>
			<% end %>
		</div>
	</div>
</div>

users_controller.rb

class UsersController < ApplicationController
  before_action :signed_in_user, only: [:index, :edit, :update, :destroy]
  before_action :correct_user, only: [:edit, :update]
  before_action :admin_user, only: [:destroy]

  def index
    @users = User.paginate(page: params[:page], per_page: 10)
  end 

  def show
  	@user = User.find(params[:id])
    @experience = current_user.experiences.build if signed_in?
    @experiences = @user.experiences.paginate(page: params[:page], per_page: 10)
  end 

  def new
  	@user = User.new
  end

  def create
  	@user = User.new(user_params)
  	if @user.save
  		redirect_to @user
  		flash[:success] = "Welcome! Happy venting!"
  	else 
  		render 'new'
  	end 
  end 

  def edit
  end

  def update
    @user = User.find(params[:id])
    if @user.update_attributes(user_params)
      flash[:success] = "Successfully updated"
      redirect_to @user
    else 
      render 'edit'
    end 
  end

  def destroy
    User.find(params[:id]).destroy
    flash[:success] = "User deleted."
    redirect_to users_url
  end

  private 

  def user_params
  	params.require(:user).permit(:name, :email, :password, :password_confirmation) #admin is not an option for security reasons
  end 

  def correct_user
    @user = User.find(params[:id])
    redirect_to(root_url) unless current_user?(@user)
  end
end

  def admin_user
    redirect_to(root_url) if !current_user.admin?
  end