title: libgdx crashes when i add dialogs
body: <p>well i am having a problem</p>
  
  <p>i've started coding my first game with libgdx and i created the menu
  i am trying to give the about button a function to open a text dialog box</p>
  
  <p>but when i add the code, the game crashes when i run it</p>
  
  <p>can anyone link me to a guide on making a text dialog?</p>
  
  <p>since everything i've found didnt work for me...</p>
  
  <p>the code i have found &amp; used :</p>
  
  <pre><code>new Dialog("Dialog", skin, "dialog") {
     protected void result (Object object) {
  
     }
  }.text("texttexttext").button("Yes", true).button("No", false).key(Keys.ENTER, true)
     .key(Keys.ESCAPE, false).show(stage);
  </code></pre>
  
  <p>stack trace</p>
  
  <pre><code>    10-11 07:41:11.051    1716-1742/com.xxx.www.android E/AndroidRuntime﹕ FATAL EXCEPTION: GLThread 60
      Process: com.xxx.www.android, PID: 1716
      com.badlogic.gdx.utils.GdxRuntimeException: No com.badlogic.gdx.scenes.scene2d.ui.Window$WindowStyle registered with name: dialog
              at com.badlogic.gdx.scenes.scene2d.ui.Skin.get(Skin.java:145)
              at com.badlogic.gdx.scenes.scene2d.ui.Dialog.&lt;init&gt;(Dialog.java:62)
              at com.xxx.www.MainMenu$2.&lt;init&gt;(MainMenu.java:104)
              at com.xxx.www.MainMenu.show(MainMenu.java:104)
              at com.badlogic.gdx.Game.setScreen(Game.java:61)
              at com.xxx.www.Splash$1.onEvent(Splash.java:72)
              at aurelienribon.tweenengine.BaseTween.callCallback(BaseTween.java:380)
              at aurelienribon.tweenengine.BaseTween.updateStep(BaseTween.java:521)
              at aurelienribon.tweenengine.BaseTween.update(BaseTween.java:424)
              at aurelienribon.tweenengine.TweenManager.update(TweenManager.java:166)
              at com.xxx.www.Splash.render(Splash.java:47)
              at com.badlogic.gdx.Game.render(Game.java:46)
              at com.xxx.www.MyGdxGame.render(MyGdxGame.java:26)
              at com.badlogic.gdx.backends.android.AndroidGraphics.onDrawFrame(AndroidGraphics.java:414)
              at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1523)
              at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)
  10-11 07:41:15.411    1716-1716/com.xxx.www.android E/AndroidGraphics﹕ waiting for pause synchronization took too long; assuming deadlock and killing
  </code></pre>