From 08bc7c393c9015e07c0ef83ea2d0a34f9baade3d Mon Sep 17 00:00:00 2001
From: Brian Zinn <github@wakeskate.com>
Date: Sat, 30 May 2020 17:46:00 -0700
Subject: [PATCH] Engine unmounted first and Engine dispose() disposes of the
 Scene.  Need an additional check before disposing the Scene #65

---
 src/Engine.tsx | 5 +++--
 src/Scene.tsx  | 4 +++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/Engine.tsx b/src/Engine.tsx
index 993c30b3..bcbd6b24 100644
--- a/src/Engine.tsx
+++ b/src/Engine.tsx
@@ -136,8 +136,9 @@ class Engine extends React.Component<EngineProps, EngineState> {
 
   componentWillUnmount () {
     window.removeEventListener('resize', this.onResizeWindow);
-    if (this.engine != null) {
-      this.engine?.dispose();
+
+    if (this.engine !== null) {
+      this.engine!.dispose();
       this.engine = null;
     }
   }
diff --git a/src/Scene.tsx b/src/Scene.tsx
index 52a88dec..a996da23 100644
--- a/src/Scene.tsx
+++ b/src/Scene.tsx
@@ -223,7 +223,9 @@ const Scene: React.FC<SceneProps> = (props: SceneProps, context?: any) => {
           scene.onPointerObservable.remove(pointerMoveObservable);
         }
 
-        scene.dispose();
+        if (scene.isDisposed === false) {
+          scene.dispose();
+        }
       }
     },
     [/* no deps, so called only on un/mount */]