From 883957688cc4aa4335e5131a60b3ac3b53290726 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 8 Aug 2018 21:42:18 -0700
Subject: [PATCH] Fix assertion failure

https://bugzilla.mozilla.org/show_bug.cgi?id=1476334
---
 src/hb-machinery-private.hh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/hb-machinery-private.hh b/src/hb-machinery-private.hh
index 119625c45..39a7fd1f6 100644
--- a/src/hb-machinery-private.hh
+++ b/src/hb-machinery-private.hh
@@ -639,7 +639,8 @@ struct hb_lazy_loader_t
 
   inline void set_stored (Stored *instance_)
   {
-    assert (instance == nullptr);
+    if (instance)
+      thiz ()->destroy (instance);
     instance = instance_;
   }