[gegl] issue #147: "Select" -> "Invert" broken when OpenCL is enabled

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 4b5abc7413f42029e68c06f7025febbc5fff5610
Author: Massimo Valentini <mvalentini335 gmail com>
Date:   Sat Apr 13 09:41:13 2019 +0200

    issue #147: "Select" -> "Invert" broken when OpenCL is enabled
    
    set a compatible format when using OpenCL

 operations/common/invert-common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/operations/common/invert-common.h b/operations/common/invert-common.h
index 9d01cc05b..a88ace184 100644
--- a/operations/common/invert-common.h
+++ b/operations/common/invert-common.h
@@ -137,7 +137,7 @@ prepare (GeglOperation *operation)
       #undef DISPATCH_MODEL
     }
 
-  if (! format)
+  if (! format || gegl_operation_use_opencl (operation))
     {
       o->user_data = PROCESS_FUNC (rgba, float);