[mutter] Fix use of uninitialized variables

[Stefan Walter <stefw src gnome org>]

commit 4608cb6027f4bfe6c7a705d085810e1dc5e25851
Author: Stef Walter <stefw redhat com>
Date:   Wed Apr 17 10:04:49 2013 +0200

    Fix use of uninitialized variables
    
    If mutter is going to -Werror by default, then it can play footloose
    and fancy free with this sorta stuff.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=698179

 src/core/prefs.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)
---
diff --git a/src/core/prefs.c b/src/core/prefs.c
index 4521264..308b947 100644
--- a/src/core/prefs.c
+++ b/src/core/prefs.c
@@ -1708,12 +1708,13 @@ meta_prefs_set_num_workspaces (int n_workspaces)
 {
   MetaBasePreference *pref;
 
-  find_pref (preferences_int, sizeof(MetaIntPreference),
-             KEY_NUM_WORKSPACES, &pref);
-
-  g_settings_set_int (SETTINGS (pref->schema),
-                      KEY_NUM_WORKSPACES,
-                      n_workspaces);
+  if (find_pref (preferences_int, sizeof(MetaIntPreference),
+                 KEY_NUM_WORKSPACES, &pref))
+    {
+      g_settings_set_int (SETTINGS (pref->schema),
+                          KEY_NUM_WORKSPACES,
+                          n_workspaces);
+    }
 }
 
 static GHashTable *key_bindings;
@@ -2216,9 +2217,11 @@ meta_prefs_set_no_tab_popup (gboolean whether)
 {
   MetaBasePreference *pref;
 
-  find_pref (preferences_bool, sizeof(MetaBoolPreference),
-             KEY_NO_TAB_POPUP, &pref);
-  g_settings_set_boolean (SETTINGS (pref->schema), KEY_NO_TAB_POPUP, whether);
+  if (find_pref (preferences_bool, sizeof(MetaBoolPreference),
+                 KEY_NO_TAB_POPUP, &pref))
+    {
+      g_settings_set_boolean (SETTINGS (pref->schema), KEY_NO_TAB_POPUP, whether);
+    }
 }
 
 int