[devhelp] fix build error for missing private struct

[Carlos Soriano <csoriano src gnome org>]

commit 9946209fb75d90526a8dba2e640e5dd43097d6d3
Author: Günther Wagner <info gunibert de>
Date:   Thu Aug 30 21:22:48 2018 +0200

    fix build error for missing private struct
    
    this slipped accidentally in during merge

 src/dh-app.c | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/src/dh-app.c b/src/dh-app.c
index ceda548b..b7979b9e 100644
--- a/src/dh-app.c
+++ b/src/dh-app.c
@@ -86,7 +86,6 @@ new_window_cb (GSimpleAction *action,
                gpointer       user_data)
 {
         DhApp *self = DH_APP (user_data);
-        DhAppPrivate *priv = dh_app_get_instance_private (self);
         GtkWidget *new_window;
 
         save_active_main_window_gsettings (self);