relay: don't query unknown authors if we have none to query

Signed-off-by: William Casarin <jb55@jb55.com>

src/app.rs

@@ -375,6 +375,7 @@ fn handle_eose(damus: &mut Damus, subid: &str, relay_url: &str) -> Result<()> {
         let txn = Transaction::new(&damus.ndb)?;
         let authors = get_unknown_author_ids(&txn, damus, 0)?;
         let n_authors = authors.len();
+        if n_authors > 0 {
             let filter = Filter::new()
                 .authors(authors.iter().map(|p| Pubkey::new(*p)).collect())
                 .kinds(vec![0]);
@@ -384,6 +385,7 @@ fn handle_eose(damus: &mut Damus, subid: &str, relay_url: &str) -> Result<()> {
             );
             let msg = ClientMessage::req("profiles".to_string(), vec![filter]);
             damus.pool.send_to(&msg, relay_url);
+        }
     } else if subid == "profiles" {
         let msg = ClientMessage::close("profiles".to_string());
         damus.pool.send_to(&msg, relay_url);