Fix Internal error

src/commands/challenge.rs

@@ -240,7 +240,12 @@ pub async fn submit(ctx: Context<'_>, submission: serenity::Attachment) -> Resul
                 if !repost_here && here {
                     continue;
                 }
-                let data = data.as_object().unwrap();
+                let data = match data.as_object() {
+                    Some(data) => data,
+                    // "suggestionChannel": "..." is at root level,
+                    // and is not an object. Ignore it.
+                    None => continue,
+                };
                 if !data.contains_key("submissionChannel") {
                     continue;
                 }