recent_topics: Improve behaviour of inplace rerender.

We used to hide and show topic rows in the DOM when topics are
updated. This resulted in incorrect calculations in the length of
visible topics. As a consequence, focus is sometimes set to hidden topic.
Removing hidden topics from DOM helps us keep
the calculations correct.

The fixes bugs related to focus being lost when trying to mute
or mark as read the last row.

static/js/list_widget.js

@@ -172,7 +172,9 @@ export function create($container, list, opts) {
         return undefined;
     }
 
-    const widget = {};
+    const widget = {
+        meta,
+    };
 
     widget.get_current_list = function () {
         return meta.filtered_list;