[babl] babl: change how conversion computers (own) error

[Øyvind Kolås <ok src gnome org>]

commit 8869eee16d054aa4ec7d189d703a536088f7fac6
Author: Øyvind Kolås <pippin gimp org>
Date:   Thu Aug 31 05:09:09 2017 +0200

    babl: change how conversion computers (own) error

 babl/babl-conversion.c |   10 ++--------
 1 files changed, 2 insertions(+), 8 deletions(-)
---
diff --git a/babl/babl-conversion.c b/babl/babl-conversion.c
index 14567e1..6a0a523 100644
--- a/babl/babl-conversion.c
+++ b/babl/babl-conversion.c
@@ -463,14 +463,8 @@ babl_conversion_error (BablConversion *conversion)
   Babl *fmt_source;
   Babl *fmt_destination;
 
-  const Babl *fmt_rgba_double = babl_format_new (babl_model ("RGBA"),
-                                                 babl_type ("double"),
-                                                 babl_component ("R"),
-                                                 babl_component ("G"),
-                                                 babl_component ("B"),
-                                                 babl_component ("A"),
-                                                 NULL);
-
+  const Babl *fmt_rgba_double = babl_format_with_space ("RGBA double",
+                                                 conversion->destination->format.space);
   double  error       = 0.0;
   long    ticks_start = 0;
   long    ticks_end   = 0;