[template-glib] template: add assertion for return types and errors

[Christian Hergert <chergert src gnome org>]

commit bcd5dcdde465378a9f0722a26f97aa91dfc2426a
Author: Christian Hergert <chergert redhat com>
Date:   Tue Aug 9 14:29:10 2016 -0700

    template: add assertion for return types and errors

 src/tmpl-template.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/tmpl-template.c b/src/tmpl-template.c
index 12cb8df..e5ac490 100644
--- a/src/tmpl-template.c
+++ b/src/tmpl-template.c
@@ -477,6 +477,8 @@ tmpl_template_expand (TmplTemplate  *self,
   if (local_scope != NULL)
     tmpl_scope_unref (local_scope);
 
+  g_assert (state.result == TRUE || (state.error == NULL || *state.error != NULL));
+
   return state.result;
 }