MavenJobWithDetails behaves different than JobWithDetails for methods

[khmarbaise]

In MavenJobWithDetails those methods return null instead of MavenBuild.BUILD_HAS_NEVER_RAN in accordance with JobWithDetails methods which return Build.BUILD_HAS_NEVER_RAN.

   public MavenBuild getLastBuild();
   public MavenBuild getLastCompletedBuild();
   public MavenBuild getLastFailedBuild();
   public MavenBuild getLastStableBuild();
   public MavenBuild getLastSuccessfulBuild();
   public MavenBuild getLastUnstableBuild();
   public MavenBuild getLastUnsuccessfulBuild();