group_idが取得できない

前提・実現したいこと

group_idの取得

ユーザー登録したら、グループ登録できる仕様なのですが
グループ登録がcreateされる前にエラーの画面が出てしまって
group_idが取得できていないとの内容でした。

発生している問題・エラーメッセージ

https://gyazo.com/7a70f0952a285d231f2487f7fcde618b

該当のソースコード

schema.rb

  create_table "contents", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.text "text"
    t.text "image"
    t.bigint "group_id"
    t.bigint "user_id"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["group_id"], name: "index_contents_on_group_id"
    t.index ["user_id"], name: "index_contents_on_user_id"
  end

  create_table "group_users", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.bigint "group_id"
    t.bigint "user_id"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["group_id"], name: "index_group_users_on_group_id"
    t.index ["user_id"], name: "index_group_users_on_user_id"
  end

  create_table "groups", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  create_table "users", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.string "name"
    t.string "email", default: "", null: false
    t.string "encrypted_password", default: "", null: false
    t.string "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["email"], name: "index_users_on_email", unique: true
    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
  end

  add_foreign_key "contents", "groups"
  add_foreign_key "contents", "users"
  add_foreign_key "group_users", "groups"
  add_foreign_key "group_users", "users"
end

routes.rb

Rails.application.routes.draw do
  devise_for :users
  root "groups#new"
  resources :users, only: [:index, :new, :create, :destroy]
  resources :groups, only: [:new, :create, :edit, :update] do
    resources :contents do
      resources :comments, only: :create
      collection do
        get 'search'
      end
    end
  end
end

/contents_controller.rb

class ContentsController < ApplicationController
  before_action :set_group

  def index
    @content = Content.new
    @contents = Content.includes(:user).order("created_at DESC")
  end

  def new
    @content = Content.new
    @group.users << current_user
  end

  def create
    @content = @group.contents.new(content_params)
    if @content.save
      respond_to do |format|
        format.json
      end
    else
      @contents = @group.contents.includes(:user)
      flash.now[:alert] = 'メッセージを入力してください。'
      render :index
    end
  end

  def destroy
    content = Content.find(params[:id])
    content.destroy
    redirect_to group_contents_path
  end

  def edit
    @content = Content.find(params[:id])
  end

  def update
    content = Content.find(params[:id])
    content.update(content_params)
  end

  def show
    @comment = Comment.new
    @comments = @content.comments.includes(:user)
  end

  def search
    @contents = Content.search(params[:keyword])
    # respond_to do |format|
    #   format.html
    #   format.json
    # end
  end

  private

  def content_params
    params.require(:message).permit(:content, :image).merge(user_id: current_user.id)
  end

  def set_group
    @group = Group.find(params[:group_id])
  end
end

groups_controller.rb

class GroupsController < ApplicationController
  # before_action :set_group 

  def index
  end

  def new
    @group = Group.new
    @group.users << current_user
  end

  def create
    @group = Group.new(group_params)
    if @group.save
      redirect_to group_contents_path, notice: 'グループを作成しました'
    else
      render :new
    end
  end

  def edit
    @group = Group.find(params[:id])
  end

  def update
    @group = Group.find(params[:id])
    if @group.update(group_params)
      redirect_to  group_messages_path(@group), notice: 'グループを更新しました'
    else
      render :edit
    end
  end

  private
  def group_params
    params.require(:group).permit(:name, user_ids: [])
  end

  # def set_group
  #   @group = Group.find(params[:group_id])
  # end
end

users_controller.rb

class UsersController < ApplicationController

  before_action :user_sign_in


  def index
    return nil if params[:keyword] == ""
    @users = User.where(['name LIKE ?', "%#{params[:keyword]}%"] ).where.not(id: current_user.id).limit(10)
  end

  def new
    @user = User.new
  end

  def create
    @users = @user
    if current_user.Create.new(user_params)
      redirect_to new_group_path
    else
      redirect_to new_user_registration_path
    end
  end

  def show
    user = User.find(params[:id])
    @contents = user.contents
  end

  private

  def user_params
    params.require(:user).permit(:name, :email)
  end

  def user_log_in
    @group_new = redirect_to new_group_path
  end

end