Fixes#10384
The problem was that doing the sort inside the insertRows messed up the model.
I removed it and it fixed the issues. However, it created an other issue with ordering.
The problem this time is that when populating the model at the start, we do not get the chats in order, so calculating the right position to insert a chat is difficult.
Instead, I use a setData function to just put all the chats in the items list, sort it and call it done, using the resetModel function.
I also did some clean ups.
db6af0554a