[mutter] window: Make should_be_on_all_workspaces() handle being headless

[Jonas Ådahl <jadahl src gnome org>]

commit 2c85bb41782069ab400e20885f5a05b3fe7c440f
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Sep 25 15:10:58 2017 -0400

    window: Make should_be_on_all_workspaces() handle being headless
    
    Also adds a soft assert to meta_window_is_on_primary_monitor() to make
    it easier to spot when callers might want to handle headless
    in a certain way.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=730551

 src/core/window.c |   25 ++++++++++++++++++-------
 1 files changed, 18 insertions(+), 7 deletions(-)
---
diff --git a/src/core/window.c b/src/core/window.c
index b9c07ec..1fc483d 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -2933,6 +2933,8 @@ meta_window_is_monitor_sized (MetaWindow *window)
 gboolean
 meta_window_is_on_primary_monitor (MetaWindow *window)
 {
+  g_return_val_if_fail (window->monitor, FALSE);
+
   return window->monitor->is_primary;
 }
 
@@ -4543,13 +4545,22 @@ set_workspace_state (MetaWindow    *window,
 static gboolean
 should_be_on_all_workspaces (MetaWindow *window)
 {
-  return
-    window->always_sticky ||
-    window->on_all_workspaces_requested ||
-    window->override_redirect ||
-    (meta_prefs_get_workspaces_only_on_primary () &&
-     !window->unmanaging &&
-     !meta_window_is_on_primary_monitor (window));
+  if (window->always_sticky)
+    return TRUE;
+
+  if (window->on_all_workspaces_requested)
+    return TRUE;
+
+  if (window->override_redirect)
+    return TRUE;
+
+  if (meta_prefs_get_workspaces_only_on_primary () &&
+      !window->unmanaging &&
+      window->monitor &&
+      !meta_window_is_on_primary_monitor (window))
+    return TRUE;
+
+  return FALSE;
 }
 
 void