[gimp] file-xpm: Fix warning about uninitialized format string

[Mukund Sivaraman <muks src gnome org>]

commit a70f3c61461b833c9672162dcea8eaad4bda90ab
Author: Mukund Sivaraman <muks banu com>
Date:   Mon May 13 16:37:48 2013 +0530

    file-xpm: Fix warning about uninitialized format string

 plug-ins/common/file-xpm.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/plug-ins/common/file-xpm.c b/plug-ins/common/file-xpm.c
index e093d1e..fb6bbc1 100644
--- a/plug-ins/common/file-xpm.c
+++ b/plug-ins/common/file-xpm.c
@@ -643,6 +643,12 @@ save_image (const gchar  *filename,
     case GIMP_INDEXEDA_IMAGE:
       format = gegl_buffer_get_format (buffer);
       break;
+
+    default:
+      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
+                   _("Unsupported drawable type"));
+      g_object_unref (buffer);
+      return FALSE;
     }
 
   /* allocate buffer making the assumption that ibuff is 32 bit aligned... */