[glib/fix-gdir-warning-msvc] gdir: shutup a warning when building with msvc

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 57c779dab45e25355fe85223dc3e21f1ef4d9f6a
Author: Ignacio Casal Quinteiro <qignacio amazon com>
Date:   Thu Jan 24 11:31:38 2019 +0100

    gdir: shutup a warning when building with msvc
    
    This way we avoid the warning:
    warning C4716: 'g_dir_new_from_dirp': must return a value

 glib/gdir.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/glib/gdir.c b/glib/gdir.c
index d0b2d5eed..6b85e99c8 100644
--- a/glib/gdir.c
+++ b/glib/gdir.c
@@ -189,6 +189,8 @@ g_dir_new_from_dirp (gpointer dirp)
   return dir;
 #else
   g_assert_not_reached ();
+
+  return NULL;
 #endif
 }