codegen: fix criticals when duplicating unowned instnaces

Fixes bug 632174

diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index cda89128ce047edace1624050ca1372fa5928fe1..6f4fc6c05623641b89134294d14e6ebc47cb13c9 100644 (file)
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -2622,7 +2622,7 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                                dup_function = get_ccode_ref_function ((ObjectTypeSymbol) type.data_type);
                                if (type.data_type is Interface && dup_function == null) {
                                        Report.error (source_reference, "missing class prerequisite for interface `%s', add GLib.Object to interface declaration if unsure".printf (type.data_type.get_full_name ()));
-                                       return null;
+                                       return new CCodeInvalidExpression();
                                }
                        } else if (cl != null && cl.is_immutable) {
                                // allow duplicates of immutable instances as for example strings
@@ -2646,7 +2646,7 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                        } else {
                                // duplicating non-reference counted objects may cause side-effects (and performance issues)
                                Report.error (source_reference, "duplicating %s instance, use unowned variable or explicitly invoke copy method".printf (type.data_type.name));
-                               return null;
+                               return new CCodeInvalidExpression();
                        }
 
                        return new CCodeIdentifier (dup_function);