FIX: Prevent crash when window icon texture is null (#13461)

[carsteneu]

Fixes #13461

Cinnamon crashes when using WebApps (e.g. WhatsApp installed from Brave Browser) after the app has been running for a while.

When muffin emits a notify::icon signal during idle_update_icon(), the window-list applets call create_icon_texture_for_window() which can return null in race conditions (e.g., when a WebApp window is being destroyed or its icon is unavailable).

Previously, this null value was passed directly to set_child(), causing a SIGSEGV in _clutter_actor_queue_only_relayout(self=0x0).

This fix adds a null check after create_icon_texture_for_window() and falls back to a default icon, preventing the crash.

Tried it with that fix - no crash detected.

Affected applets:

window-list@cinnamon.org
grouped-window-list@cinnamon.org

[mtwebster]

Fixed as part of d4166a1

edit: please double-check for me - this was mainly to fix wayland sessions, but may not completely have fixed the issue in x11.

[carsteneu]

Thank you very much for your Feedback - I tested your fix in X11 (Linux Mint 22.3 VM) with aggressive stress tests:

Tests:

30x rapid Firefox launch/kill with spiegel.de (heavy content page)
30x multi-app stress (calculator + nemo simultaneous)
Logs: 0 segfaults, 0 crashes
Result: ✅ Your fix works perfectly in X11.

My PR added a defensive null-check after create_icon_texture_for_window(). Your architectural fix (avoiding the call for window-backed apps) addresses the root cause and is from my point of view absolutly sufficient.

Happy to close PR #13466 since your fix covers both Wayland and X11. Let me know if you prefer we should keep the additional null-check as defense-in-depth.