Bug 1336957, use diagnostic assert for wrapper existence, r=baku

xpcom/base/CycleCollectedJSContext.cpp

@@ -1280,7 +1280,7 @@ CycleCollectedJSContext::JSObjectsTenured()
   for (auto iter = mNurseryObjects.Iter(); !iter.Done(); iter.Next()) {
     nsWrapperCache* cache = iter.Get();
     JSObject* wrapper = cache->GetWrapperPreserveColor();
-    MOZ_ASSERT(wrapper);
+    MOZ_DIAGNOSTIC_ASSERT(wrapper);
     if (!JS::ObjectIsTenured(wrapper)) {
       MOZ_ASSERT(!cache->PreservingWrapper());
       const JSClass* jsClass = js::GetObjectJSClass(wrapper);