correct

Author: jprosevear

packages/solid-router/src/router.ts

@@ -791,7 +791,7 @@ export class Router<
     if (
       typeof window !== 'undefined' &&
       'CSS' in window &&
-      typeof window.CSS.supports === 'function'
+      typeof window.CSS?.supports === 'function'
     ) {
       this.isViewTransitionTypesSupported = window.CSS.supports(
         'selector(:active-view-transition-type(a)',