Web UI: TypeError "Cannot read properties of undefined (reading 'length')" on home session list

Description

The OpenCode web UI crashes on the home page session list:
TypeError: Cannot read properties of undefined (reading 'length')

The home session-list sidebar renders e.groups().length > 0 with no null guard.
groups() can return undefined when the projects/sessions data hasn't loaded yet
during first render - a timing race on slower connections / slower JS engines.

On a fast browser (e.g. Edge) against the same server it does NOT crash
(data resolves before first render) - confirming it's a first-render race.

Plugins

None (default config)

OpenCode version

1.18.18 (latest)

Steps to reproduce

1. Run opencode web --port 4096
2. Open the web UI in a browser where the initial data load is a bit slower
   (e.g. a lightweight/mobile browser, or access remotely via a relay with extra latency)
3. Home page renders the session-list sidebar and crashes:

Screenshot and/or share link

TypeError: Cannot read properties of undefined (reading 'length')
    at get when [as when] (index-*.js:1537:15902)
    at get children [as children] (index-*.js:1537:15869)
    ...

Operating System

Windows 11 (10.0.22631)

Terminal

n/a (web UI); server started from PowerShell