title: Corona SDK gotoScene error
body: <p>So I'm making an app in Corona SDK and I'm getting an error when I click my button that is trying to load up my first level.</p>
  
  <p>Here are my codes:</p>
  
  <p>main.lua</p>
  
  <pre><code>local storyboard = require "storyboard"
  storyboard.gotoScene("menu")
  </code></pre>
  
  <p>menu.lua</p>
  
  <pre><code>local storyboard = require ("storyboard")
  local scene = storyboard.newScene()
  
  function scene:createScene( event )
  
      local screenGroup = self.view
  
      -- Background
      bg = display.newImage("images/bg.png")
      bg.x = display.contentCenterX
      bg.y = display.contentCenterY
      screenGroup:insert(bg)
  
      -- Title
      title = display.newImage("images/title.png")
      title.x = display.contentCenterX
      title.y = display.contentCenterY - 100
      screenGroup:insert(title)
  
      -- Play game
      play = display.newImage("images/playgame.png")
      play.x = display.contentCenterX - 170
      play.y = display.contentCenterY - 27
      screenGroup:insert(play)
  
      -- About Us
      about = display.newImage("images/about.png")
      about.x = display.contentCenterX - 100
      about.y = display.contentCenterY + 40
      screenGroup:insert(about)
  
      -- Level Select
      select = display.newImage("images/select.png")
      select.x = display.contentCenterX
      select.y = display.contentCenterY + 100
      screenGroup:insert(select)
  
  end
  
  function start(event)
      if event.phase == "began" then
          storyboard.gotoScene("level1", "fade", 400)
      end
  end
  
  function start2(event)
      if event.phase == "began" then
          storyboard.gotoScene("about", "fade", 400)
      end
  end
  
  function start3(event)
      if event.phase == "began" then
          storyboard.gotoScene("selectlvl", "fade", 400)
      end
  end
  
  function scene:enterScene(event)
  
      play:addEventListener("touch", start)
      about:addEventListener("touch", start2)
      select:addEventListener("touch", start3)
  
  end
  
  scene:addEventListener( "createScene", scene )
  scene:addEventListener( "enterScene", scene )
  
  return scene
  </code></pre>
  
  <p>And I have 0 code in my level1.lua</p>
  
  <p>The error that I'm getting is this:</p>
  
  <pre><code>Runtime error
      ?:0: attempt to concatenate global 'sceneName' (a nil value)
  stack traceback:
      [C]: ?
      ?: in function 'gotoScene'
      ...s\corona projects\stickman obsticale course\menu.lua.42: in function
  &lt;...s\corona projects\stickman obsticale course\menu.
  </code></pre>
  
  <p>Thanks for reading and I hope you can find an answer, because I can't :)</p>