[vala/0.40] codegen: Avoid critical trying to serialize an unsupported type to Variant

[Rico Tzschichholz <ricotz src gnome org>]

commit 6543470b45a65d0e828f54c488c164b74c97fa94
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Mar 30 08:47:17 2020 +0200

    codegen: Avoid critical trying to serialize an unsupported type to Variant
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/952

 codegen/valagvariantmodule.vala | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/codegen/valagvariantmodule.vala b/codegen/valagvariantmodule.vala
index 3fa5ab507..dc4b10502 100644
--- a/codegen/valagvariantmodule.vala
+++ b/codegen/valagvariantmodule.vala
@@ -521,6 +521,7 @@ public class Vala.GVariantModule : GAsyncModule {
 
                if (result == null) {
                        Report.error (type.source_reference, "GVariant deserialization of type `%s' is not 
supported".printf (type.to_string ()));
+                       return new CCodeInvalidExpression ();
                }
 
                return result;
@@ -813,6 +814,7 @@ public class Vala.GVariantModule : GAsyncModule {
 
                if (result == null) {
                        Report.error (type.source_reference, "GVariant serialization of type `%s' is not 
supported".printf (type.to_string ()));
+                       return new CCodeInvalidExpression ();
                }
 
                return result;