RailsでデータがあるはずかNilになってしまう

Controlに下記のようなコードを記入したのですがlocalhost:3000/chatにアクセスしても　NoMethodError in ChatController#index
undefined method `id' for nil:NilClass　と出てしまいます。 他のページでは正常に表示されるのですがなぜかindexでは正常に表示されません。 確認したところちゃんとログインも出来た状態でした。

chat_controller.rb

class ChatController < ApplicationController
    def create
      current_user_chat_rooms = ChatRoomUser.where(user_id: current_user.id).map(&:chat_room)
      chat_room = ChatRoomUser.where(chat_room: current_user_chat_rooms, user_id: params[:user_id]).map(&:chat_room).first
      if chat_room.blank?
        chat_room = ChatRoom.create
        ChatRoomUser.create(chat_room: chat_room, user_id: current_user.id)
        ChatRoomUser.create(chat_room: chat_room, user_id: params[:user_id])
      end
      redirect_to action: :show, id: chat_room.id
    end
    def index
      @current_user =  User.find_by(user_id: params[:user_id])
      @chat_rooms = ChatRoom.joins(:chat_room_users).
        where("chat_room_users.user_id =?", @current_user.id)
    end


    def show
      chat_room = ChatRoom.find_by(id: params[:id])
      @current_user = User.find_by(id: session[:user_id])
      @chat_room_user = chat_room.chat_room_users.
        where.not(user_id: current_user.id).first.user
      @chat_room_myuser = chat_room.chat_room_users.
        where.not(user_id: current_user.id).last.user
      @chat_rooms = ChatRoom.joins(:chat_room_users).
        where("chat_room_users.user_id =?", @current_user.id)
      @chat_messages = ChatMessage.where(chat_room: chat_room).order(:created_at)
    end
  end

chat_room.rb

class ChatRoom < ApplicationRecord
    has_many :chat_messages
    has_many :chat_room_users
end

chat_room_user.rb

class ChatRoomUser < ApplicationRecord
    belongs_to :chat_room
    belongs_to :user
end

index.html.erb

<% @chat_rooms.each do |e| %>
<%= e.id %>
<% end %>

show.html.erb

<% provide(:title, @chat_room_user.username ) %>
<div class="container center">
  <div class="sidebar">
    <%= link_to root_path(), method: :get do%>
    <div class="home-btn">
    <%= image_tag 'right-nav/home', class: 'home-img' %>
    <span class="home-p">ホーム</span>
    </div>
    <% end %>
    <%= link_to home_path(), method: :get do%>
    <div class="global-btn">
    <%= image_tag 'right-nav/global', class: 'global-img'%>
    <span class="global-p">グローバル</span>
    </div>
    <% end %>
    <% if current_user.try(:admin?) %>
    <%= link_to rails_admin_path(), method: :get do%>
    <div class="control-btn">
    <%= image_tag 'right-nav/control.svg', class: 'control-img'%>
    <span class="control-p">管理画面</span>
    </div>
    <% end %>
    <% end %>
    <div class="group-btn">
    <%= image_tag 'right-nav/group', class: 'group-img'%>
    <span class="group-p">グループ</span>
    </div>
  </div>
<div class="main">
<% if @chat_room_myuser.id == @chat_room_user.id %>
  <header class="header">
    <div class="chatPartner">
      <img src="<%= @chat_room_user.image %>" class="dm-icon">
      <div class="dm-username"><%= @chat_room_user.username %></div>
      <div class="dm-userid">@<%= @chat_room_user.user_id %></div>
    </div>
  </header>
<div class="chat-history">
<%= render @chat_messages %>
<% @chat_rooms.each do |e| %>
<%= e.id %>
<% end %>
</div>
  <div class="text-box">
  <form class="messageInputForm">
    <div class="container">
      <input type="text" data-behavior="room_speaker" class="messageInputForm_input" placeholder="メッセージを入力...">
    </div>
  </form>
  </div>
</div>
</div>

<% else %>
<div class="error-message">
<p class="sorry-chat">Sorry</p>
<p class="sorry-text">ページを表示する権限がありません</p>
</div>
<% end %>