Remove 'null' from lobby when the user is not logged in

The inline javascript is trying to append an element that only exists
when the user is logged in, resulting in viewing "null" instead when
they are not logged in. Moreover, when the window size changes, a series
of nulls are rendered.

ui/lobby/src/lobby.inline.ts

@@ -14,7 +14,7 @@ function layout() {
   cols = newCols;
   document
     .querySelector<HTMLElement>(cols > 2 ? '.lobby__side' : '.lobby')
-    ?.append(document.querySelector('.lobby__timeline')!);
+    ?.append(document.querySelector('.lobby__timeline') ?? '');
 }
 
 layout();