fix: fix type errors

src/components/PostCard.astro

@@ -16,7 +16,7 @@ interface Props {
 	published: Date;
 	updated?: Date;
 	tags: string[];
-	category: string;
+	category: string | null;
 	image: string;
 	description: string;
 	draft: boolean;

src/components/PostMeta.astro

@@ -10,7 +10,7 @@ interface Props {
 	published: Date;
 	updated?: Date;
 	tags: string[];
-	category: string;
+	category: string | null;
 	hideTagsForMobile?: boolean;
 	hideUpdateDate?: boolean;
 }

src/utils/url-utils.ts

@@ -21,7 +21,7 @@ export function getTagUrl(tag: string): string {
 	return url(`/archive/?tag=${encodeURIComponent(tag.trim())}`);
 }
 
-export function getCategoryUrl(category: string): string {
+export function getCategoryUrl(category: string | null): string {
 	if (
 		!category ||
 		category.trim() === "" ||