title: NullPointerException on MovieCreator().build android unity plugin
body: <p>I am using mp4parser in my app to merge audio and video which is working fine in android. But when I make .aar file and add the plugin in unity it throws a NullPointerException.</p>
  
  <p>Here is the log</p>
  
  <pre>
  java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.InputStream.close()' on a null object reference 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.coremedia.iso.PropertyBoxParserImpl.(PropertyBoxParserImpl.java:67) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.coremedia.iso.IsoFile.(IsoFile.java:59) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.googlecode.mp4parser.authoring.container.mp4.MovieCreator.build(MovieCreator.java:49) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.googlecode.mp4parser.authoring.container.mp4.MovieCreator.build(MovieCreator.java:38) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.actvt.showdown.pluggin.Mp4ParserAudioMuxer.mux(Mp4ParserAudioMuxer.java:31)
   12-20 13:47:07.409 9171-10512/? W/System.err: at com.actvt.showdown.pluggin.Utils.mergeAudioAndVideo(Utils.java:217) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.actvt.showdown.pluggin.Utils.access$400(Utils.java:44) 
  12-20 13:47:07.409 9171-10512/? W/System.err: at com.actvt.showdown.pluggin.Utils$1.run(Utils.java:200) 
  12-20 13:47:07.410 9171-10512/? W/System.err: at java.lang.Thread.run(Thread.java:761)
  </pre>
  
  <p>When I do</p>
  
  <pre><code>video = new MovieCreator().build(videoFile);
  </code></pre>
  
  <p>It is not finding a isoparser-default.properties file in the jar or something like that? I'm using this jar to use mp4 parser in unity3d pluggin android native code.</p>