[gnome-todo] sidebar: Add missing include

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 227b4f529edc22a71de8e4570b14d4cebf4956ce
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sun Jun 9 01:07:09 2019 -0300

    sidebar: Add missing include

 src/sidebar/gtd-sidebar.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/sidebar/gtd-sidebar.h b/src/sidebar/gtd-sidebar.h
index b98673a..9609865 100644
--- a/src/sidebar/gtd-sidebar.h
+++ b/src/sidebar/gtd-sidebar.h
@@ -22,6 +22,8 @@
 
 #include <gtk/gtk.h>
 
+#include "gtd-panel.h"
+
 G_BEGIN_DECLS
 
 #define GTD_TYPE_SIDEBAR (gtd_sidebar_get_type())