[gnome-builder] gui: be defensive against NULL error

[Christian Hergert <chergert src gnome org>]

commit 6ade58f64ea804c6d367b94ca9dcb09b9f0f185f
Author: Christian Hergert <chergert redhat com>
Date:   Sat Aug 31 09:37:02 2019 -0700

    gui: be defensive against NULL error
    
    Related #1028

 src/libide/gui/ide-frame.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/src/libide/gui/ide-frame.c b/src/libide/gui/ide-frame.c
index 5387944ec..6a2ac9dfd 100644
--- a/src/libide/gui/ide-frame.c
+++ b/src/libide/gui/ide-frame.c
@@ -1061,7 +1061,9 @@ ide_frame_close_page_cb (GObject      *object,
 
   if (!ide_page_agree_to_close_finish (page, result, &error))
     {
-      g_message ("%s", error->message);
+      g_message ("%s does not agree to close: %s",
+                 G_OBJECT_TYPE_NAME (page),
+                 error ? error->message : "No reason");
       return;
     }