add needed variables for error page

app/controllers/beers_controller.rb

@@ -32,6 +32,7 @@ class BeersController < ApplicationController
         format.html { redirect_to beers_path, notice: "Beer was successfully created." }
         format.json { render :show, status: :created, location: @beer }
       else
+        @breweries = Brewery.all
         format.html { render :new, status: :unprocessable_entity }
         format.json { render json: @beer.errors, status: :unprocessable_entity }
       end