[pan2] Fix error found by valgrind: 216 (192 direct, 24 indirect) bytes in 1 blocks are definitely lost in

[Petr Kovář <pmkovar src gnome org>]

commit 1bdde462b87861aed58cf7450f3c1ab8d49e2e78
Author: Olaf Seibert <rhialto falu nl>
Date:   Tue Mar 22 00:09:34 2016 +0100

    Fix error found by valgrind: 216 (192 direct, 24 indirect) bytes in 1 blocks are definitely lost in loss 
record 10,554 of 11,336
    
      at 0x6AC0493: g_type_create_instance (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4600.2)
       by 0x6AA238A: ??? (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4600.2)
       by 0x6AA3C70: g_object_newv (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4600.2)
       by 0x6AA45A3: g_object_new (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4600.2)
       by 0x5165188: gtk_label_new (in /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0.2400.28)
       by 0x47548B: init_colors (pan.cc:831)
       by 0x47548B: main (pan.cc:954)
    
    Since the widget is not top-level, nor in a container, gtk_widget_destroy () will not deref it.

 pan/gui/pan.cc |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/pan/gui/pan.cc b/pan/gui/pan.cc
index 91d1030..b7c4490 100644
--- a/pan/gui/pan.cc
+++ b/pan/gui/pan.cc
@@ -866,7 +866,9 @@ namespace
     fg_col = GroupPrefs::color_to_string(def_fg);
     bg_col = GroupPrefs::color_to_string(def_bg);
 
+    g_object_ref_sink (r);
     gtk_widget_destroy (r);
+    g_object_unref (r);
 
     PanColors& c (PanColors::get());
     c.def_fg = fg_col;