WebXRManager: Improve timing when .isPresenting is changed.

src/renderers/webxr/WebXRManager.js

@@ -95,10 +95,10 @@ function WebXRManager( renderer, gl ) {
 		renderer.setRenderTarget( renderer.getRenderTarget() ); // Hack #15830
 		animation.stop();
 
-		scope.dispatchEvent( { type: 'sessionend' } );
-
 		scope.isPresenting = false;
 
+		scope.dispatchEvent( { type: 'sessionend' } );
+
 	}
 
 	function onRequestReferenceSpace( value ) {
@@ -108,10 +108,10 @@ function WebXRManager( renderer, gl ) {
 		animation.setContext( session );
 		animation.start();
 
-		scope.dispatchEvent( { type: 'sessionstart' } );
-
 		scope.isPresenting = true;
 
+		scope.dispatchEvent( { type: 'sessionstart' } );
+
 	}
 
 	this.setFramebufferScaleFactor = function ( /* value */ ) {