Potenail NPE in org.apache.hadoop.classification.tools

Hello,
Our code analyses found the following potential NPE:

  private static Object process(Object obj, Class<?> type) {
    if (obj == null) {
      return null;
    }

  public static boolean start(RootDoc root) {
    System.out.println(
        ExcludePrivateAnnotationsStandardDoclet.class.getSimpleName());
    RootDoc excludedDoc = RootDocProcessor.process(root);
    if (excludedDoc.specifiedPackages().length == 0) { // NPE
      return true;
    }

Full Trace:

1. Return null to caller
https://github.com/apache/hadoop/blob/f40e3eb0590f85bb42d2471992bf5d524628fdd6/hadoop-common-project/hadoop-annotations/src/main/java/org/apache/hadoop/classification/tools/RootDocProcessor.java#L61

2. Return the return value of function process to caller
https://github.com/apache/hadoop/blob/f40e3eb0590f85bb42d2471992bf5d524628fdd6/hadoop-common-project/hadoop-annotations/src/main/java/org/apache/hadoop/classification/tools/RootDocProcessor.java#L56

3. Function process executes and stores the return value to excludedDoc (excludedDoc can be null)
https://github.com/apache/hadoop/blob/f40e3eb0590f85bb42d2471992bf5d524628fdd6/hadoop-common-project/hadoop-annotations/src/main/java/org/apache/hadoop/classification/tools/ExcludePrivateAnnotationsStandardDoclet.java#L41

4. excludedDoc is passed as the this pointer to function com.sun.javadoc.RootDoc.specifiedPackages (excludedDoc can be null)
https://github.com/apache/hadoop/blob/f40e3eb0590f85bb42d2471992bf5d524628fdd6/hadoop-common-project/hadoop-annotations/src/main/java/org/apache/hadoop/classification/tools/ExcludePrivateAnnotationsStandardDoclet.java#L42

Commit: f40e3eb0590f85bb42d2471992bf5d524628fdd6