[gnome-system-monitor] Fix memory leak in gsm_tree_view_load_state()

[Robert Roth <robertroth src gnome org>]

commit 658f99615ef11c8a5b8512ac78eff27658b56b92
Author: Eric R. Schulz <eric ers35 com>
Date:   Thu Aug 18 16:59:30 2016 -0400

    Fix memory leak in gsm_tree_view_load_state()
    
    Match call to gtk_tree_view_get_columns() with g_list_free().
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770116

 src/treeview.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/treeview.c b/src/treeview.c
index 491f9d4..819ecbd 100644
--- a/src/treeview.c
+++ b/src/treeview.c
@@ -182,6 +182,8 @@ gsm_tree_view_load_state (GsmTreeView *tree_view)
             g_free (key);
         }
 
+        g_list_free (columns);
+
         gtk_widget_show_all (header_menu);
 
         g_settings_get (priv->settings, "columns-order", "ai", &var_iter);