fix: 404 page styling for nested pages (closes #458)

quartz/components/Head.tsx

@@ -1,4 +1,4 @@
-import { joinSegments, pathToRoot } from "../util/path"
+import { FullSlug, _stripSlashes, joinSegments, pathToRoot } from "../util/path"
 import { JSResourceToScriptElement } from "../util/resources"
 import { QuartzComponentConstructor, QuartzComponentProps } from "./types"
 
@@ -7,7 +7,11 @@ export default (() => {
     const title = fileData.frontmatter?.title ?? "Untitled"
     const description = fileData.description?.trim() ?? "No description provided"
     const { css, js } = externalResources
-    const baseDir = pathToRoot(fileData.slug!)
+
+    const url = new URL(`https://${cfg.baseUrl ?? "example.com"}`)
+    const path = url.pathname as FullSlug
+    const baseDir = fileData.slug === "404" ? path : pathToRoot(fileData.slug!)
+
     const iconPath = joinSegments(baseDir, "static/icon.png")
     const ogImagePath = `https://${cfg.baseUrl}/static/og-image.png`