title: Jung2: NullPointerException "AWT-EventQueue-0" labelVertex(BasicVertexLabelRenderer.java:84)
body: <p>When jung2 2.1 renders my graph in
  rc.getVertexLabelTransformer().apply(v) (BasicRenderer.java, 74)
  it takes my v object (not null, it has correct not null toString) and returns null that cause the exception in other place. How to fix it ?</p>
  
  <p>PS I use Scala but doubt it affected. 
  Code and report <a href="https://github.com/jrtom/jung/issues/60" rel="nofollow">https://github.com/jrtom/jung/issues/60</a></p>