[libgit2-glib] submodule: use g_return_val_if_fail to fix the build

[Ignacio Casal Quinteiro <icq src gnome org>]

commit f62565bba44816b19c20751b01bcaa2f7111e4ca
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Fri Dec 19 10:49:03 2014 +0100

    submodule: use g_return_val_if_fail to fix the build

 libgit2-glib/ggit-submodule.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/libgit2-glib/ggit-submodule.c b/libgit2-glib/ggit-submodule.c
index 3a4deec..d75d47d 100644
--- a/libgit2-glib/ggit-submodule.c
+++ b/libgit2-glib/ggit-submodule.c
@@ -102,8 +102,8 @@ ggit_submodule_open (GgitSubmodule  *submodule,
        git_repository *repo;
        gint ret;
 
-       g_return_if_fail (submodule != NULL);
-       g_return_if_fail (error == NULL || *error == NULL);
+       g_return_val_if_fail (submodule != NULL, NULL);
+       g_return_val_if_fail (error == NULL || *error == NULL, NULL);
 
        ret = git_submodule_open (&repo, submodule->submodule);