315940 fix a crash in nsNavHistoryResultNode::GetParent by initializing mParent to nsnull in ctor, along with a few other vars that are unusued. r=brettw

browser/components/places/src/nsNavHistoryResult.cpp

@@ -85,7 +85,8 @@ inline PRInt32 CompareIntegers(PRUint32 a, PRUint32 b)
 NS_IMPL_ISUPPORTS2(nsNavHistoryResultNode,
                    nsNavHistoryResultNode, nsINavHistoryResultNode)
 
-nsNavHistoryResultNode::nsNavHistoryResultNode() : mID(0), mExpanded(PR_FALSE)
+nsNavHistoryResultNode::nsNavHistoryResultNode() : mID(0), mExpanded(PR_FALSE), 
+  mParent(nsnull), mAccessCount(0), mTime(0)
 {
 }