Return 404 on missing static file in todo example.

examples/todo/src/static_files.rs

@@ -1,8 +1,7 @@
-use rocket::response::NamedFile;
-use std::io;
 use std::path::{Path, PathBuf};
+use rocket::response::NamedFile;
 
 #[get("/<path..>", rank = 5)]
-fn all(path: PathBuf) -> io::Result<NamedFile> {
-    NamedFile::open(Path::new("static/").join(path))
+fn all(path: PathBuf) -> Option<NamedFile> {
+    NamedFile::open(Path::new("static/").join(path)).ok()
 }