[vala] codegen: Don't try to create a GClosure for null

[Jürg Billeter <juergbi src gnome org>]

commit 341808e8f62ca78aab856dc01a0c51669883742f
Author: Evan Nemerson <evan coeus-group com>
Date:   Sat Oct 16 09:57:35 2010 +0200

    codegen: Don't try to create a GClosure for null
    
    Fixes bug 631269.

 codegen/valaccodemethodcallmodule.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/codegen/valaccodemethodcallmodule.vala b/codegen/valaccodemethodcallmodule.vala
index cceec70..2aeca59 100644
--- a/codegen/valaccodemethodcallmodule.vala
+++ b/codegen/valaccodemethodcallmodule.vala
@@ -364,7 +364,7 @@ public class Vala.CCodeMethodCallModule : CCodeAssignmentModule {
 									closure_new.add_argument (new CCodeCastExpression (cexpr, "GCallback"));
 									closure_new.add_argument (delegate_target);
 									closure_new.add_argument (delegate_target_destroy_notify);
-									cexpr = closure_new;
+									cexpr = new CCodeConditionalExpression (new CCodeBinaryExpression (CCodeBinaryOperator.EQUALITY, cexpr, new CCodeIdentifier ("NULL")), new CCodeIdentifier ("NULL"), closure_new);
 								} else {
 									carg_map.set (get_param_pos (param.cdelegate_target_parameter_position), delegate_target);
 									if (deleg_type.value_owned) {