[gnome-settings-daemon] wacom: don't unref null objects

[William Jon McCann <mccann src gnome org>]

commit 6d486385c245c758186c9ecc786635e3a76ab49b
Author: William Jon McCann <jmccann redhat com>
Date:   Mon Nov 22 22:16:17 2010 -0500

    wacom: don't unref null objects
    
    Fixes a crash.

 plugins/wacom/gsd-wacom-manager.c |   30 ++++++++++++++++++++----------
 1 files changed, 20 insertions(+), 10 deletions(-)
---
diff --git a/plugins/wacom/gsd-wacom-manager.c b/plugins/wacom/gsd-wacom-manager.c
index be2d8f3..9314ef1 100644
--- a/plugins/wacom/gsd-wacom-manager.c
+++ b/plugins/wacom/gsd-wacom-manager.c
@@ -608,20 +608,30 @@ gsd_wacom_manager_stop (GsdWacomManager *manager)
                 p->device_manager = NULL;
         }
 
-        g_object_unref (p->wacom_settings);
-        p->wacom_settings = NULL;
+        if (p->wacom_settings != NULL) {
+                g_object_unref (p->wacom_settings);
+                p->wacom_settings = NULL;
+        }
 
-        g_object_unref (p->stylus_settings);
-        p->stylus_settings = NULL;
+        if (p->stylus_settings != NULL) {
+                g_object_unref (p->stylus_settings);
+                p->stylus_settings = NULL;
+        }
 
-        g_object_unref (p->eraser_settings);
-        p->eraser_settings = NULL;
+        if (p->eraser_settings != NULL) {
+                g_object_unref (p->eraser_settings);
+                p->eraser_settings = NULL;
+        }
 
-        g_object_unref (p->cursor_settings);
-        p->cursor_settings = NULL;
+        if (p->cursor_settings != NULL) {
+                g_object_unref (p->cursor_settings);
+                p->cursor_settings = NULL;
+        }
 
-        g_object_unref (p->pad_settings);
-        p->pad_settings = NULL;
+        if (p->pad_settings != NULL) {
+                g_object_unref (p->pad_settings);
+                p->pad_settings = NULL;
+        }
 }
 
 static void