From 1aa21343992de65460febdeda528f25a652972d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lars=20K=C3=BChne?= <lakuehne@gmail.com>
Date: Sun, 3 Nov 2002 08:37:00 +0000
Subject: [PATCH] fixed NPE

---
 .../com/puppycrawl/tools/checkstyle/TreeWalker.java      | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/checkstyle/com/puppycrawl/tools/checkstyle/TreeWalker.java b/src/checkstyle/com/puppycrawl/tools/checkstyle/TreeWalker.java
index 75e674ea7..f2b391865 100644
--- a/src/checkstyle/com/puppycrawl/tools/checkstyle/TreeWalker.java
+++ b/src/checkstyle/com/puppycrawl/tools/checkstyle/TreeWalker.java
@@ -130,8 +130,13 @@ class TreeWalker
     {
         mMessages.reset();
         notifyBegin(aContents);
-        aAST.setParent(null);
-        process(aAST);
+
+         // empty files are not flagged by javac, will yield aAST == null
+        if (aAST != null) {
+            aAST.setParent(null);
+            process(aAST);
+        }
+
         notifyEnd();
     }