[gimp] app: fix OVERLAY mode so it gets fed linear data

[Øyvind Kolås <ok src gnome org>]

commit 4a3fbb8f3549d98c2b7c1fe1712e46303d80a129
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Jan 23 18:04:07 2017 +0100

    app: fix OVERLAY mode so it gets fed linear data

 app/core/gimp-layer-modes.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/app/core/gimp-layer-modes.c b/app/core/gimp-layer-modes.c
index 10236e8..b4508b3 100644
--- a/app/core/gimp-layer-modes.c
+++ b/app/core/gimp-layer-modes.c
@@ -97,8 +97,9 @@ gimp_layer_mode_is_linear (GimpLayerMode  mode)
       return FALSE;
 
     case GIMP_LAYER_MODE_COLOR_ERASE:
-    case GIMP_LAYER_MODE_OVERLAY:
       return FALSE;
+    case GIMP_LAYER_MODE_OVERLAY:
+      return TRUE;
 
     case GIMP_LAYER_MODE_LCH_HUE:
     case GIMP_LAYER_MODE_LCH_CHROMA: