actually delete chats in clearChats()

Signed-off-by: Jared Van Bortel <jared@nomic.ai>

gpt4all-chat/chatlistmodel.h

@@ -196,6 +196,7 @@ public:
         m_newChat = nullptr;
         m_serverChat = nullptr;
         m_currentChat = nullptr;
+        for (auto * chat: m_chats) { delete chat; }
         m_chats.clear();
     }