[gimp/metadata-browser] file-png: Display a readable string when error message is unavailable

[Roman Joost <romanofski src gnome org>]

commit ec8da3076e63e5ab8680ebb20a07b9813f23d687
Author: Mukund Sivaraman <muks banu com>
Date:   Tue Dec 6 20:48:09 2011 +0530

    file-png: Display a readable string when error message is unavailable

 plug-ins/common/file-png.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plug-ins/common/file-png.c b/plug-ins/common/file-png.c
index 157ff7a..ad678c6 100644
--- a/plug-ins/common/file-png.c
+++ b/plug-ins/common/file-png.c
@@ -1893,7 +1893,7 @@ save_dialog (gint32    image_ID,
       gchar *display_name = g_filename_display_name (ui_file);
 
       g_printerr (_("Error loading UI file '%s': %s"),
-                  display_name, error ? error->message : "???");
+                  display_name, error ? error->message : _("Unknown error"));
 
       g_free (display_name);
     }