Ammo physics raycast fix

Related to https://forum.babylonjs.com/t/ammojsplugin-raycast-function-broken/2190

src/Physics/Plugins/ammoJSPlugin.ts

@@ -86,6 +86,8 @@ export class AmmoJSPlugin implements IPhysicsEnginePlugin {
 
         this._tmpAmmoConcreteContactResultCallback = new this.bjsAMMO.ConcreteContactResultCallback();
         this._tmpAmmoConcreteContactResultCallback.addSingleResult = () => { this._tmpContactCallbackResult = true; };
+        
+        this._raycastResult = new PhysicsRaycastResult();
 
         // Create temp ammo variables
         this._tmpAmmoTransform = new this.bjsAMMO.btTransform();