flatten bruh

crates/engine/tree/src/tree/root.rs

@@ -368,7 +368,7 @@ where
             body.transactions()
                 .iter()
                 .flat_map(|tx| [tx.recover_signer(), tx.kind().to().copied()])
-                .filter_map(|address| address),
+                .flatten()
         );
         if let Some(withdrawals) = body.withdrawals() {
             accounts.extend(withdrawals.iter().map(|withdrawal| withdrawal.address));