messagesadapter: clear cached convId once current account is changed

Gitlab: #158
Change-Id: I126ab29e1d63e036d68a62d293abf6f445a60722

src/messagesadapter.cpp

@@ -44,6 +44,7 @@ void
 MessagesAdapter::safeInit()
 {
     connect(&LRCInstance::instance(), &LRCInstance::currentAccountChanged, [this]() {
+        currentConvUid_.clear();
         connectConversationModel();
     });
     connectConversationModel();