[balsa/gtk4] filter-export-callbacks: Build with gtk4

[Peter Bloomfield <peterb src gnome org>]

commit 68f0fbe1ac7842ab988ef7b7931513fd5469b566
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Sat Oct 24 18:17:44 2020 -0400

    filter-export-callbacks: Build with gtk4

 src/filter-export-callbacks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/filter-export-callbacks.c b/src/filter-export-callbacks.c
index eeb531c51..b41ed98d6 100644
--- a/src/filter-export-callbacks.c
+++ b/src/filter-export-callbacks.c
@@ -70,5 +70,5 @@ fex_dialog_response(GtkWidget * dialog, gint response, gpointer data)
                                             fex_dialog_response_func,
                                             NULL);
     }
-    gtk_widget_destroy(dialog);
+    gtk_window_destroy(GTK_WINDOW(dialog));
 }