When connection is too fast, `this.scroller` used before it is initialized

[TheV360]

This is because there's a chance that the websocket returns results before DOMContentLoaded fires, so that the sidebar never gets a chance to run its onload method. This usually happens with locally-hosted instances, which is often frustrating!

Uncaught TypeError: this.scroller is null
    display_messages sbs2/src/sidebar.js:203
    pull_recent sbs2/src/activity.js:203
    handle_response sbs2/src/socket.js:338
    onmessage sbs2/src/socket.js:284
    start_websocket sbs2/src/socket.js:277
    immediate sbs2/src/main.js:52
    <anonymous> sbs2/src/main.js:11
sidebar.js:203:3

One fix is relatively simple:

diff --git a/src/activity.js b/src/activity.js
index 64bfa80..a547993 100644
--- a/src/activity.js
+++ b/src/activity.js
@@ -200,7 +200,7 @@ let Act = {
 			
 			/// sidebar messages ///
 			// TODO: ensure that these are displayed BEFORE any websocket new messages
-			Sidebar.display_messages(objects.message, true)
+			do_when_ready(_=>Sidebar.display_messages(objects.message, true))
 			
 			/// activity tab ///
 			for (let act of objects.activity)