[gimp] app: small fix in gimpbrushcore-kernels.h

[Ell <ell src gnome org>]

commit cbe40000f58c9b25d081ce2144dd13a51c2fc488
Author: Ell <ell_se yahoo com>
Date:   Wed Feb 6 15:12:26 2019 -0500

    app: small fix in gimpbrushcore-kernels.h

 app/paint/gimpbrushcore-kernels.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/paint/gimpbrushcore-kernels.h b/app/paint/gimpbrushcore-kernels.h
index 32503ef56e..ea5eb4530c 100644
--- a/app/paint/gimpbrushcore-kernels.h
+++ b/app/paint/gimpbrushcore-kernels.h
@@ -34,7 +34,7 @@ struct Kernel<guchar>
   static constexpr value_type
   round (accum_type x)
   {
-    return (x + 127) / 256;
+    return (x + 128) / 256;
   }
 };