Added missing release_object.

diff --git a/server/queue.c b/server/queue.c
index 48edb23..a441fdb 100644
--- a/server/queue.c
+++ b/server/queue.c
@@ -1051,6 +1051,7 @@
              win != filter_win && !is_child_window( filter_win, win )))
         {
             clear_bits &= ~get_hardware_msg_bit( msg );
+            release_object( win_thread );
             msg = msg->next;
             continue;
         }