fix window on destroy

src/routes/portfolio/+page.svelte

@@ -5,6 +5,7 @@
 	import AddStock from '../../components/AddStock.svelte';
 	import { getRequest } from '../../utils/api.js';
 	import { goto } from '$app/navigation';
+	import { browser } from '$app/environment';
 
 	let portfolioId = undefined;
 	let result = [];
@@ -31,7 +32,9 @@
 	}
 
 	onMount(() => {
-		window.addEventListener('keydown', handleKeyDown);
+		if (browser) {
+			window.addEventListener('keydown', handleKeyDown);
+		}
 
 		return authentication.subscribe(async (auth) => {
 			if (!auth || !auth.token) {
@@ -44,7 +47,9 @@
 	});
 
 	onDestroy(() => {
-		window.removeEventListener('keydown', handleKeyDown);
+		if (browser) {
+			window.removeEventListener('keydown', handleKeyDown);
+		}
 	});
 
 	async function fetchPortfolio() {