Fix building with check-lisp-object-type

* src/thread.c (mark_one_thread): Use NILP to compare with
m_saved_last_thing_searched, which is a Lisp object.  Reported by
Andreas Politz <politza@hochschule-trier.de>.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/thread.c b/src/thread.c
index dda262984c0..b2f8561f923 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -540,7 +540,7 @@ mark_one_thread (struct thread_state *thread)
 
   mark_object (thread->m_last_thing_searched);
 
-  if (thread->m_saved_last_thing_searched)
+  if (!NILP (thread->m_saved_last_thing_searched))
     mark_object (thread->m_saved_last_thing_searched);
 }