По умолчанию у иконки будет пустой alt (но не undefined!)

src/lib/components/HoverIcon.svelte

@@ -4,7 +4,7 @@
 	let className: string = '';
 	export { className as class };
 	export let src: string | null = null;
-	export let alt: string | undefined = undefined;
+	export let alt: string = "";
 	export let size: number = 32;
 	export let black: boolean = false;