fix some memory leaks

mailnews/db/msgdb/src/nsDBFolderInfo.cpp

@@ -197,7 +197,7 @@ nsresult nsDBFolderInfo::InitFromExistingDB()
 					if (ret == NS_OK)
 					{
 						ret = rowCursor->NextRow(m_mdb->GetEnv(), &m_mdbRow, &rowPos);
-						rowCursor->Release();
+						rowCursor->CutStrongRef(m_mdb->GetEnv());
 						if (ret == NS_OK && m_mdbRow)
 						{
 							LoadMemberVariables();

mailnews/db/msgdb/src/nsMsgDatabase.cpp

@@ -336,6 +336,12 @@ nsMsgDatabase::~nsMsgDatabase()
 		NS_RELEASE(m_HeaderParser);
 		m_HeaderParser = nsnull;
 	}
+	if (m_mdbAllMsgHeadersTable)
+		m_mdbAllMsgHeadersTable->Release();
+
+	if (m_mdbAllThreadsTable)
+		m_mdbAllThreadsTable->Release();
+
 	if (m_mdbEnv)
 	{
 		m_mdbEnv->CutStrongRef(m_mdbEnv); //??? is this right?
@@ -1574,6 +1580,8 @@ nsMsgDBEnumerator::nsMsgDBEnumerator(nsMsgDatabase* db,
 
 nsMsgDBEnumerator::~nsMsgDBEnumerator()
 {
+	if (mRowCursor)
+		mRowCursor->CutStrongRef(mDB->GetEnv());
     NS_RELEASE(mDB);
 	NS_IF_RELEASE(mResultHdr);
 }
@@ -1702,6 +1710,7 @@ NS_IMETHODIMP nsMsgDatabase::ListAllKeys(nsMsgKeyArray &outputKeys)
 			if (err == NS_OK)
 				outputKeys.Add(outOid.mOid_Id);
 		}
+		rowCursor->Release();
 	}
 	return err;
 }

mailnews/db/msgdb/src/nsMsgThread.cpp

@@ -748,8 +748,12 @@ nsresult nsMsgThread::ChangeChildCount(PRInt32 delta)
 	nsresult ret = NS_OK;
 	PRUint32 childCount = 0;
 	m_mdbDB->RowCellColumnToUInt32(m_metaRow, m_mdbDB->m_threadChildrenColumnToken, childCount);
+
+	NS_ASSERTION(childCount != 0 || delta > 0, "child count gone negative");
 	childCount += delta;
 
+	NS_ASSERTION((PRInt32) childCount >= 0, "child count gone to 0 or below");
+
 	ret = m_mdbDB->UInt32ToRowCellColumn(m_metaRow, m_mdbDB->m_threadChildrenColumnToken, childCount);
 	return ret;
 }