now throw 404 error page if the final number doesn't exists

src/main.rs

@@ -85,7 +85,7 @@ fn show_post(title: String) -> Template {
     let mut context = get_context();
 
     let title_splited: Vec<&str> = title.split('-').collect();
-    let id = title_splited.last().unwrap().parse().unwrap();
+    let id = title_splited.last().unwrap().parse().unwrap_or_else(|_| -1);
 
     match get_post(id) {
         Ok(mut post) => {