[gimp] app: clean up Luminance blend function

[Ell <ell src gnome org>]

commit 1dd3d7e91e290ff75a833bdd296230fe7e0696b4
Author: Ell <ell_se yahoo com>
Date:   Mon Jun 10 10:53:00 2019 -0400

    app: clean up Luminance blend function
    
    ... in particular, don't use a static fish.

 .../layer-modes/gimpoperationlayermode-blend.c          | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)
---
diff --git a/app/operations/layer-modes/gimpoperationlayermode-blend.c 
b/app/operations/layer-modes/gimpoperationlayermode-blend.c
index f88a87a8ef..73b8f4abab 100644
--- a/app/operations/layer-modes/gimpoperationlayermode-blend.c
+++ b/app/operations/layer-modes/gimpoperationlayermode-blend.c
@@ -911,15 +911,14 @@ gimp_operation_layer_mode_blend_luminance (GeglOperation *operation,
                                            gfloat        *comp,
                                            gint           samples)
 {
-  static const Babl *fish;
-  gfloat            *scratch;
-  gfloat            *in_Y;
-  gfloat            *layer_Y;
-  const Babl *format = gegl_operation_get_source_format (operation, "input");
-  const Babl *space  = gegl_operation_get_source_space (operation, "input");
-
-  fish  = babl_fish (babl_format_with_space ("RGBA float", space),
-            babl_format_with_space ("Y float", space));
+  const Babl *fish;
+  gfloat     *scratch;
+  gfloat     *in_Y;
+  gfloat     *layer_Y;
+  const Babl *space = gegl_operation_get_source_space (operation, "input");
+
+  fish = babl_fish (babl_format_with_space ("RGBA float", space),
+                    babl_format_with_space ("Y float",    space));
 
   scratch = gegl_scratch_new (gfloat, 2 * samples);