[regression] Cinnamon segfaults if workspaces-only-on-primary is enabled

[autarkper]

Ever since pull #1831 was merged, I am experiencing that Cinnamon segfaults if the setting "workspaces-only-on-primary" is enabled. If the setting is enabled from start, Cinnamon will appear to start cleanly but will crash about a second after displaying the desktop. Enabling the setting within a Cinnamon session will crash Cinnamon instantly.

Restarting will not help until the setting is disabled, so think twice before trying to reproduce the issue.

I am convinced that the segfault is indirectly caused by the creation of a dummy Meta.Window object, which is a work-around for a muffin function, get_mouse_window, not accepting a null parameter. See the aforementioned pull request for more information.

NB: The number of monitors is not important.

Affected Cinnamon versions: 1.7.4/1.7.5 and up.