[recipes] Silence a compiler warning

[Matthias Clasen <matthiasc src gnome org>]

commit bf7af741136bb4830db441ed2838cbd273399fa0
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jul 15 15:01:50 2017 -0400

    Silence a compiler warning

 src/gr-app.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gr-app.c b/src/gr-app.c
index f019b94..a266cba 100644
--- a/src/gr-app.c
+++ b/src/gr-app.c
@@ -69,7 +69,7 @@ gr_app_activate (GApplication *app)
                 win = GTK_WINDOW (gr_window_new (GR_APP (app)));
         gtk_window_present (win);
 
-        gr_window_show_surprise (win);
+        gr_window_show_surprise (GR_WINDOW (win));
 }
 
 static void