Crash unmanaging windows on secondary monitor when “workspaces-only-on-primary”

This is a follow-up on bug 792818 where mutter would crash in x11/session code while saving the state of windows on secondary monitor when “workspaces-only-on-primary”

Now it aborts a bit further in meta_window_unmanage() because the window being unmanaged is not removed from the workspace->windows list:

(gdb) bt
#0  0x00007fc4c609d54b in raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/pt-raise.c:37
#1  0x0000000000402adc in dump_gjs_stack_on_signal_handler (signo=6) at main.c:373
#2  0x00007fc4c609d680 in <signal handler called> () at /usr/lib64/libpthread-2.17.so
#3  0x00007fc4c5cf71b7 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#4  0x00007fc4c5cf88a8 in __GI_abort () at abort.c:90
#5  0x00007fc4c6520aa5 in g_assertion_message (domain=domain@entry=0x7fc4cc55d2b3 "mutter", file=file@entry=0x7fc4cc567762 "core/window.c", line=line@entry=1520, func=func@entry=0x7fc4cc569970 <__FUNCTION__.106598> "meta_window_unmanage", message=message@entry=0xe624c0 "assertion failed: (g_list_find (workspace->windows, window) == NULL)") at gtestutils.c:2436
#6  0x00007fc4c6520b3a in g_assertion_message_expr (domain=domain@entry=0x7fc4cc55d2b3 "mutter", file=file@entry=0x7fc4cc567762 "core/window.c", line=line@entry=1520, func=func@entry=0x7fc4cc569970 <__FUNCTION__.106598> "meta_window_unmanage", expr=expr@entry=0x7fc4cc568940 "g_list_find (workspace->windows, window) == NULL") at gtestutils.c:2459
#7  0x00007fc4cc50b0cb in meta_window_unmanage (window=window@entry=0x2511240 [MetaWindowX11], timestamp=timestamp@entry=0)
    at core/window.c:1520
#8  0x00007fc4cc4eb950 in meta_display_unmanage_windows_for_screen (display=<optimized out>, screen=<optimized out>, timestamp=0)
    at core/display.c:2688
#9  0x00007fc4cc4fb70f in meta_screen_free (screen=0xc626c0 [MetaScreen], timestamp=0) at core/screen.c:845
#10 0x00007fc4cc4ebe5e in meta_display_close (display=0xe416e0 [MetaDisplay], timestamp=timestamp@entry=0) at core/display.c:1133
#11 0x00007fc4cc4f6f60 in meta_run () at core/main.c:297
#12 0x00007fc4cc4f6f60 in meta_run () at core/main.c:654
#13 0x0000000000402584 in main (argc=1, argv=0x7ffd73420118) at main.c:539

(gdb) f 7
#7  0x00007fc4cc50b0cb in meta_window_unmanage (window=window@entry=0x2511240 [MetaWindowX11], timestamp=timestamp@entry=0)
    at core/window.c:1520
1520	      g_assert (g_list_find (workspace->windows, window) == NULL);

(gdb) list
1515	  tmp = window->screen->workspaces;
1516	  while (tmp != NULL)
1517	    {
1518	      MetaWorkspace *workspace = tmp->data;
1519	
1520	      g_assert (g_list_find (workspace->windows, window) == NULL);
1521	      g_assert (g_list_find (workspace->mru_list, window) == NULL);
1522	
1523	      tmp = tmp->next;
1524	    }

(gdb) p window->workspace
$7 = 0x0

(gdb) p window->on_all_workspaces
$8 = 0

So I suspect when unmanaging the window, calling set_workspace_state (window, FALSE, NULL); we leave set_workspace_state() before actually removing the window from all workspaces because of this:

4682	
4683	  if (on_all_workspaces == window->on_all_workspaces &&
4684	      workspace == window->workspace &&
4685	      !window->constructing)
4686	    return;