message_list_data: Track if the data is rendered using message list id.

This is an easy way to track if a MessageListData is rendered.
Storing MessageList object would make us liable to cleanup the
MessageList object when the data is no longer in use.

Note that this is more like "likely / past rendered message list id",
we will have to check currently rendered message list data to verify
if the data object is really rendered.

web/src/message_lists.ts

@@ -97,6 +97,7 @@ export function set_current(msg_list: MessageList | undefined): void {
 function delete_message_list(message_list: MessageList): void {
     message_list.view.$list.remove();
     rendered_message_lists.delete(message_list.id);
+    message_list.data.set_rendered_message_list_id(undefined);
 }
 
 export function update_current_message_list(msg_list: MessageList | undefined): void {