[gnome-shell] shell-global: Only set the scale factor if get_setting succeeded

[Jasper St. Pierre <jstpierre src gnome org>]

commit 29addc499ca0f8dc5bf9cf6d18eaaa01a5c2b985
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sat Feb 22 18:00:57 2014 -0500

    shell-global: Only set the scale factor if get_setting succeeded
    
    If gdk_screen_get_setting fails, like if it's running without XSettings,
    then the GValue will have a value of 0. A lot of code tries to divide by
    the scale factor. This produces NaN, and combined with the fact that NaN
    is "leaky", we very quickly end up spinning out of control.

 src/shell-global.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/shell-global.c b/src/shell-global.c
index 7e0ac8b..59b5273 100644
--- a/src/shell-global.c
+++ b/src/shell-global.c
@@ -756,8 +756,8 @@ update_scale_factor (GdkScreen *screen, gpointer data)
   GValue value = G_VALUE_INIT;
 
   g_value_init (&value, G_TYPE_INT);
-  gdk_screen_get_setting (global->gdk_screen, "gdk-window-scaling-factor", &value);
-  g_object_set (context, "scale-factor", g_value_get_int (&value), NULL);
+  if (gdk_screen_get_setting (global->gdk_screen, "gdk-window-scaling-factor", &value))
+    g_object_set (context, "scale-factor", g_value_get_int (&value), NULL);
 }
 
 /* This is an IBus workaround. The flow of events with IBus is that every time