[baobab] window: fix style

[Stefano Facchini <sfacchini src gnome org>]

commit 1e712b4ec2186682ca3baa69cd07ef7ddfe64bd8
Author: Stefano Facchini <stefano facchini gmail com>
Date:   Fri Oct 27 16:39:10 2017 +0200

    window: fix style

 src/baobab-window.vala |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/baobab-window.vala b/src/baobab-window.vala
index 5e8f9da..5165d05 100644
--- a/src/baobab-window.vala
+++ b/src/baobab-window.vala
@@ -185,11 +185,13 @@ namespace Baobab {
 
             set_ui_state (home_page, false);
 
-            button_press_event.connect ( (event) => {
+            button_press_event.connect ((event) => {
+                // mouse back button
                 if (event.button == 8) {
                     lookup_action ("show-home-page").activate (null);
+                    return Gdk.EVENT_STOP;
                 }
-                return false;
+                return Gdk.EVENT_PROPAGATE;
             });
 
             show ();