[gnome-builder] style: fix styling in stacksidebar

[Christian Hergert <chergert src gnome org>]

commit 840c39d42694f7abdb88a7d8814f2cd9b5e09643
Author: Christian Hergert <chergert redhat com>
Date:   Tue Feb 16 14:32:48 2016 -0800

    style: fix styling in stacksidebar

 data/theme/Adwaita-shared.css |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/theme/Adwaita-shared.css b/data/theme/Adwaita-shared.css
index cd6127e..d78bec9 100644
--- a/data/theme/Adwaita-shared.css
+++ b/data/theme/Adwaita-shared.css
@@ -73,6 +73,7 @@ omnisearchdisplay omnisearchgroup omnisearchrow:selected {
  */
 workbench preferences stacksidebar list {
   border-right: 1px solid alpha(@borders, 0.4);
+  background-color: @theme_base_color;
 }
 workbench preferences preferencesgroup list row {
   padding: 10px;