[gimp] app: propagate the error when the XCF to save cannot even be created.

[Jehan Pagès <jehanp src gnome org>]

commit f6fb13378dd264b93d00235a8778606e43c67648
Author: Jehan <jehan girinstud io>
Date:   Sat Jul 11 16:28:19 2015 +0200

    app: propagate the error when the XCF to save cannot even be created.
    
    The possible failure of `g_file_replace()` was overlooked, as well as
    the error which may have been created and could be useful information
    for the developers.

 app/xcf/xcf.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/app/xcf/xcf.c b/app/xcf/xcf.c
index e5946b9..bbcf09d 100644
--- a/app/xcf/xcf.c
+++ b/app/xcf/xcf.c
@@ -416,6 +416,12 @@ xcf_save_invoker (GimpProcedure         *procedure,
       if (progress)
         gimp_progress_end (progress);
     }
+  else
+    {
+      g_propagate_prefixed_error (error, my_error,
+                                  _("Error creating '%s': "),
+                                  filename);
+    }
 
   g_free (filename);
   g_object_unref (file);