RubyonRails プルダウンのrenderエラーについて

Question

前提・実現したいこと

railsの学習をしております。
登録処理でValidationにかかった後のrenderで
select_tagがエラーになります。
※その他の項目は入力値がそのまま残っています
form_forでhtmlを組み立てていますが
プルダウンについてはモデルと関連性がないため
select_tagを使用しています。
やり方が間違っていないか、
解決方法をご教授いただければ幸甚です。

登録画面表示:
EmployeeController#new

登録処理:
EmployeeController#create

発生している問題・エラーメッセージ

undefined method `map' for nil:NilClass
<%= select_tag :store1, options_from_collection_for_select(@storeAll, :id, :name), prompt: "選択してください", class: "form-control" %>

該当のソースコード

db/schema.rb

# employees：社員管理テーブル
# responsibles:社員管理テーブルと拠点テーブルの中間テーブル
# stores:拠点テーブル

ActiveRecord::Schema.define(version: 2018_12_02_020333) do

  create_table "employees", force: :cascade do |t|
    t.string "name"
    t.string "email"
    t.date "birthday"
    t.date "joinday"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "password_digest"
    t.string "sex"
  end

  create_table "responsibles", force: :cascade do |t|
    t.integer "order"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "employee_id"
    t.integer "store_id"
    t.index ["employee_id"], name: "index_responsibles_on_employee_id"
    t.index ["store_id"], name: "index_responsibles_on_store_id"
  end

  create_table "stores", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

end

app/model/employee.rb

class Employee < ApplicationRecord
  has_secure_password
  has_many :responsibles
  has_many :stores, through: :responsibles
  accepts_nested_attributes_for :responsibles

  validates :name, {presence: true, length: { maximum: 30 }}
  validates :email, {presence: true, uniqueness: true}
  validates :password, {presence: true, length: { minimum: 6 }}
end

app/model/responsible.rb

class Responsible < ApplicationRecord
  belongs_to :employee
  belongs_to :store
end

app/model/store.rb

class Store < ApplicationRecord
  has_many :responsibles
  has_many :employees, through: :responsibles
end

app/config/routes.rb

Rails.application.routes.draw do
  get "employee/new" => "employee#new"
  post "employee/create" => "employee#create"
end

app/Controllers/employee_Controller.rb

class EmployeeController < ApplicationController

  # 新規登録画面表示
  def new
    @employee = Employee.new
    @storeAll = Store.all
  end

  # 新規登録
  def create
    # 社員情報を登録
    @employee = Employee.new
    @employee.name = params[:name]
    @employee.email = params[:email]
    @employee.password = params[:password]
    @employee.sex = params[:sex]
    @employee.birthday = params[:birthday]
    @employee.joinday = params[:joinday]

    # 担当拠点1を登録
    if params[:store1].present?
      setResponsible(params[:store1], 1)
    end

    if @employee.save
      flash[:notice] = "新規作成しました"
      redirect_to("/employee/index")
    else
      render("employee/new")
    end
  end
end

app/views/employee/new.html.erb

<% @employee.errors.full_messages.each do |message| %>
  <div class="pt-xl-2"></div>
  <div class="alert alert-danger" role="alert">
    ・<%= message %>
  </div>
<% end %>
<div class="mx-auto pt-xl-5" style="width:600px;">
  <%= form_for(@employee, url: {controller: "employee", action:"create" }) do |f| %>
    <h1>Create</h1>
    <div class="form-label-group pt-xl-4">
      <%= f.label :inputName, "名前" %>
      <%= f.text_field :name, id:"inputName",class: "form-control", placeholder: "名前", autocomplete:"new-name", required: true, autofocus:true %>
    </div>
    <div class="form-label-group pt-xl-3">
      <%= f.label :inputEmail, "Email" %>
      <%= f.text_field :email, id:"inputEmail",type:"email", class: "form-control", placeholder: "Email", autocomplete:"new-email", required: true %>
    </div>
    <div class="form-label-group pt-xl-3">
      <%= f.label :inputPassword, "Password" %>
      <%= f.text_field :password, id:"inputPassword",type:"password", class: "form-control", placeholder: "Password", autocomplete:"new-password", required: true %>
    </div>
    <div class="form-label-group pt-xl-3">
      <%= f.label :inputSex, "性別" %>
    </div>
    <div class="btn-group btn-group-toggle" data-toggle="buttons">
      <label class="btn btn-secondary active">
        <%= f.radio_button :sex, :M, id:"inputSexM" %> 男
      </label>
      <label class="btn btn-secondary">
        <%= f.radio_button :sex, :F, id:"inputSexF" %> 女
      </label>
    </div>
    <div class="form-label-group pt-xl-3">
      <%= f.label :inputStore1, "担当拠点1" %>
    </div>
    <div>
       <%= select_tag :store1, options_from_collection_for_select(@storeAll, :id, :name), prompt: "選択してください", class: "form-control" %>
    </div>
    <div class="pt-xl-5 mb-lg-5">
      <%= f.submit :create, class:"btn btn-lg btn-primary btn-block" %>
    </div>
  <% end %>
</div>

試したこと

view
storeAll→Store.all

before:
<%= select_tag :store1, options_from_collection_for_select(@storeAll, :id, :name), prompt: "選択してください", class: "form-control" %>
after:
<%= select_tag :store1, options_from_collection_for_select(Store.all, :id, :name), prompt: "選択してください", class: "form-control" %>

補足情報（FW/ツールのバージョンなど）

開発端末：macOS Mojave

$ rails -v

Rails 5.2.1

$ ruby -v

ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin18]

Answer 1

@storeAll変数をelseでも定義してください。

    if @employee.save
      flash[:notice] = "新規作成しました"
      redirect_to("/employee/index")
    else
      @storeAll = Store.all
      render("employee/new")
    end