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

[Robert Roth <robertroth src gnome org>]

commit a4582506642bb4728453fef88450db07cf7cfd60
Author: Eric R. Schulz <eric ers35 com>
Date:   Thu Aug 18 17:00:16 2016 -0400

    Fix memory leak in cb_main_window_state_changed()
    
    Match call to g_settings_get_string() with g_free().
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770116

 src/interface.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/interface.cpp b/src/interface.cpp
index afae95c..809de89 100644
--- a/src/interface.cpp
+++ b/src/interface.cpp
@@ -616,6 +616,7 @@ cb_main_window_state_changed (GtkWidget *window, GdkEventWindowState *event, gpo
             disks_thaw (app);
         }
     }
+    g_free (current_page);
     return FALSE;
 }