output: #fixed code
                                private void incrementalCompile( Set<Object> drivers )
    {
      for( Object driver: drivers )
      {
        //noinspection unchecked
        Set<IFile> files = ((Collection<File>)ReflectUtil.method( driver, "getResourceFiles" ).invoke() ).stream().map( (File f) -> ManifoldHost.getFileSystem().getIFile( f ) )
          .collect( Collectors.toSet() );
        for( ITypeManifold tm : ManifoldHost.instance().getCurrentModule().getTypeManifolds() )
        {
          for( IFile file: files )
          {
            Set<String> types = Arrays.stream( tm.getTypesForFile( file ) ).collect( Collectors.toSet() );
            if( types.size() > 0 )
            {
              ReflectUtil.method( driver, "mapTypesToFile", Set.class, File.class ).invoke( types, file.toJavaFile() );
              for( String fqn : types )
              {
                // This call surfaces the type in the compiler.  If compiling in "static" mode, this means
                // the type will be compiled to disk.
                IDynamicJdk.instance().getTypeElement( _tp.getContext(), (JCTree.JCCompilationUnit)_tp.getCompilationUnit(), fqn );
              }
            }
          }
        }
      }
    }
input: #vulnerable code 
                                private void incrementalCompile( Set<Object> drivers )
    {
      JavacElements elementUtils = JavacElements.instance( _tp.getContext() );
      for( Object driver: drivers )
      {
        //noinspection unchecked
        Set<IFile> files = ((Collection<File>)ReflectUtil.method( driver, "getResourceFiles" ).invoke() ).stream().map( (File f) -> ManifoldHost.getFileSystem().getIFile( f ) )
          .collect( Collectors.toSet() );
        for( ITypeManifold tm : ManifoldHost.instance().getCurrentModule().getTypeManifolds() )
        {
          for( IFile file: files )
          {
            Set<String> types = Arrays.stream( tm.getTypesForFile( file ) ).collect( Collectors.toSet() );
            if( types.size() > 0 )
            {
              ReflectUtil.method( driver, "mapTypesToFile", Set.class, File.class ).invoke( types, file.toJavaFile() );
              for( String fqn : types )
              {
                // This call surfaces the type in the compiler.  If compiling in "static" mode, this means
                // the type will be compiled to disk.
                elementUtils.getTypeElement( fqn );
              }
            }
          }
        }
      }
    } 
                              #location 9 
                              #vulnerability type NULL_DEREFERENCE