[tepl] AbstractFactoryVala: fix warning about incompatible pointer type

[Sébastien Wilmet <swilmet src gnome org>]

commit 4ccd6e9c7f04f8fdb2e32ee529a5f09cdcf8491e
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Feb 21 12:41:06 2018 +0100

    AbstractFactoryVala: fix warning about incompatible pointer type
    
    Now g_object_ref() propagates the type.
    
    There were no bugs, TeplAbstractFactoryVala is a subclass of
    TeplAbstractFactory.

 tepl/tepl-abstract-factory-vala.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/tepl/tepl-abstract-factory-vala.c b/tepl/tepl-abstract-factory-vala.c
index 96dc1b9..5e65175 100644
--- a/tepl/tepl-abstract-factory-vala.c
+++ b/tepl/tepl-abstract-factory-vala.c
@@ -100,7 +100,7 @@ tepl_abstract_factory_vala_set_singleton_vala (TeplAbstractFactoryVala *factory_
 {
        g_return_if_fail (TEPL_IS_ABSTRACT_FACTORY_VALA (factory_vala));
 
-       tepl_abstract_factory_set_singleton (g_object_ref (factory_vala));
+       tepl_abstract_factory_set_singleton (g_object_ref (TEPL_ABSTRACT_FACTORY (factory_vala)));
 }
 
 /**