[gegl] operations: Fix a neglected color variation in mosaic.c

[Téo Mazars <teom src gnome org>]

commit 736c8122e410a07e86e60b2acc098fd00f1bdc33
Author: Téo Mazars <teo mazars ensimag fr>
Date:   Sun Sep 22 11:34:10 2013 +0200

    operations: Fix a neglected color variation in mosaic.c
    
    for the non-averaging case

 operations/common/mosaic.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/operations/common/mosaic.c b/operations/common/mosaic.c
index 69fbd9a..c67c187 100644
--- a/operations/common/mosaic.c
+++ b/operations/common/mosaic.c
@@ -2098,8 +2098,8 @@ fill_poly_image (Polygon             *poly,
                               else
                                 pixel = buf[b] + (gint) ((mdatas->fore[b] - buf[b]) * contrib);
 
-                              /*  factor in per-tile intensity variation but alpha*/
-                              if (NB_CPN < 4)
+                              /* factor in per-tile intensity variation but alpha */
+                              if (b < NB_CPN - 1)
                                 pixel += vary;
 
                               pixel = CLAMP (pixel, 0.0, 1.0);