icon url in config should not prevent zulip from starting

[jschauma]

Describe the bug

It seems that if I have a missing "icon" in my domain.json configuration, Zulip will not start -- it opens, but then spin-wheels instead of connecting to the configured server, with no packets being sent to the server. To work around that, I had to add

"icon": "https://chat.zulip.org/static/images/logo/zulip-icon-128x128.271d0f6a0ca2.png",

to the configuration file.

Since version 5.9.5, that stopped working, too. After much troubleshooting, it turned out that downloading that file and using a local pathname for the "icon" configuration works:

"icon": "/Users/jschauma/Library/Application Support/Zulip/zulip-logo.png",

IMO, the application should not fail silently to load the domain configuration if an icon is missing and instead either display a meaningful error ("missing icon in config X", "icon URL must be a local file", ...), or, better, simply start up and deal with not having an icon.

To Reproduce

Edit ~/Library/Application Support/Zulip/config/domain.json and remove the "icon" option or set it to a URL.

Expected behavior

Opening Zulip starts and connects to the server.

Desktop (please complete the following information):

• Operating System:
  macOS Monterey (12.6.3)
  Darwin hostname 21.6.0 Darwin Kernel Version 21.6.0: Mon Dec 19 20:46:01 PST 2022; root:xnu-8020.240.18~2/RELEASE_ARM64_T8101 arm64

• Zulip Desktop Version: 5.9.5