[vala] Fix use of nullable GLib.Value

[Jürg Billeter <juergbi src gnome org>]

commit 9682426693ec1d16b05856098482c9b36fa5335d
Author: Jürg Billeter <j bitron ch>
Date:   Thu Jun 25 15:04:29 2009 +0200

    Fix use of nullable GLib.Value

 codegen/valaccodebasemodule.vala |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index 925d9b5..dfd11cc 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -3616,6 +3616,7 @@ internal class Vala.CCodeBaseModule : CCodeModule {
 
 		bool gvalue_boxing = (target_type != null
 		                      && target_type.data_type == gvalue_type
+		                      && !(expression_type is NullType)
 		                      && expression_type.get_type_id () != "G_TYPE_VALUE");
 
 		if (expression_type.value_owned