From 094e7140964facd6d0e1412e0594207a3383c37e Mon Sep 17 00:00:00 2001
From: Andrew Garrett <agarrett@wikimedia.org>
Date: Mon, 13 Aug 2012 15:57:57 +0100
Subject: [PATCH] Fix for bug 39085

Edits to talk pages were being compared to the previous revision e ven when there was no previous revision.

Change-Id: Id45575dca2ec121fc469019ad9384d035af96d51
---
 includes/DiscussionParser.php | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/includes/DiscussionParser.php b/includes/DiscussionParser.php
index 03a55747b..d4e2fdf69 100644
--- a/includes/DiscussionParser.php
+++ b/includes/DiscussionParser.php
@@ -122,9 +122,15 @@ abstract class EchoDiscussionParser {
 		$userID = $revision->getUser();
 		$userName = $revision->getUserText();
 		$user = $userID != 0 ? User::newFromId( $userID ) : User::newFromName( $userName, false );
-		$prevRevision = Revision::newFromId( $revision->getParentId() );
+		$prevText = '';
+		if ( $revision->getParentId() ) {
+			$prevRevision = Revision::newFromId( $revision->getParentId() );
+			if ( $prevRevision ) {
+				$prevText = $prevRevision->getText();
+			}
+		}
 
-		$changes = self::getMachineReadableDiff( $prevRevision->getText(), $revision->getText() );
+		$changes = self::getMachineReadableDiff( $prevText, $revision->getText() );
 		$output = self::interpretDiff( $changes, $user->getName() );
 
 		self::$revisionInterpretationCache[$revision->getID()] = $output;