fix crash on exit in nsMsgSearchSession destructor, 313357 sr=mscott

mailnews/base/search/src/nsMsgLocalSearch.cpp

@@ -125,11 +125,9 @@ nsMsgSearchBoolExpression::nsMsgSearchBoolExpression (nsMsgSearchBoolExpression
 
 nsMsgSearchBoolExpression::~nsMsgSearchBoolExpression()
 {
-    // we must recursively destroy all sub expressions before we destroy ourself.....We leave search terms alone!
-    if (m_leftChild)
-        delete m_leftChild;
-    if (m_rightChild)
-        delete m_rightChild;
+  // we must recursively destroy all sub expressions before we destroy ourself.....We leave search terms alone!
+  delete m_leftChild;
+  delete m_rightChild;
 }
 
 nsMsgSearchBoolExpression *
@@ -590,7 +588,7 @@ nsresult nsMsgSearchOfflineMail::MatchTerms(nsIMsgDBHdr *msgToMatch,
                                             PRUint32 headerSize,
                                             PRBool Filtering,
                                             nsMsgSearchBoolExpression ** aExpressionTree,
-											PRBool *pResult) 
+                                            PRBool *pResult) 
 {
   NS_ENSURE_ARG(aExpressionTree);
   nsresult err;

mailnews/base/search/src/nsMsgSearchSession.cpp

@@ -96,6 +96,7 @@ nsMsgSearchSession::AddSearchTerm(nsMsgSearchAttribValue attrib,
 	m_termList->AppendElement (pTerm);
         // force the expression tree to rebuild whenever we change the terms
         delete m_expressionTree;
+        m_expressionTree = nsnull;
 	return NS_OK;
 }
 
@@ -105,6 +106,7 @@ nsMsgSearchSession::AppendTerm(nsIMsgSearchTerm *aTerm)
     NS_ENSURE_ARG_POINTER(aTerm);
     NS_ENSURE_TRUE(m_termList, NS_ERROR_NOT_INITIALIZED);
     delete m_expressionTree;
+    m_expressionTree = nsnull;
     return m_termList->AppendElement(aTerm);
 }
 
@@ -648,7 +650,6 @@ void nsMsgSearchSession::DestroyScopeList()
 
 void nsMsgSearchSession::DestroyTermList ()
 {
-    delete m_expressionTree;
     m_termList->Clear();
 }