[gimp] app: fixing 2 argument type build warnings.

[Jehan Pagès <jehanp src gnome org>]

commit 8fee058c1fb8219db2f8eb80dacbde572e5362e4
Author: Jehan <jehan girinstud io>
Date:   Wed Mar 29 15:20:25 2017 +0200

    app: fixing 2 argument type build warnings.
    
    Introduced in commit 5e7d9d8 and completely overlooked by myself!

 app/dialogs/quit-dialog.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/app/dialogs/quit-dialog.c b/app/dialogs/quit-dialog.c
index aa7addf..5337286 100644
--- a/app/dialogs/quit-dialog.c
+++ b/app/dialogs/quit-dialog.c
@@ -378,7 +378,7 @@ quit_close_all_dialog_container_changed (GimpContainer *images,
        * one's mind and not exist after the last save, for instance by
        * hitting Esc quickly while the last save is in progress.
        */
-      g_idle_add (quit_close_all_idle, private);
+      g_idle_add ((GSourceFunc) quit_close_all_idle, private);
     }
   else
     {
@@ -608,7 +608,7 @@ quit_close_all_dialog_query_tooltip (GtkWidget  *widget,
 static gboolean
 quit_close_all_idle (QuitDialog *private)
 {
-  gtk_dialog_response (private->dialog, GTK_RESPONSE_OK);
+  gtk_dialog_response (GTK_DIALOG (private->dialog), GTK_RESPONSE_OK);
 
   return FALSE;
 }