024177cecb
Previously, desktop-shell would only create its internal shell_seat object for each seat available when the desktop-shell module is loaded. This is a problem any time seats are created dynamically. In particular, the Wayland and RDP backends create seats on an as-needed basis and they weren't getting picked up proprely by desktop-shell. Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=77649