don't iterate slot_list if zero-lamport (#16678)

runtime/src/accounts_db.rs

@@ -1570,8 +1570,7 @@ impl AccountsDb {
                                         self.accounts_index
                                             .roots_and_ref_count(&locked_entry, max_clean_root),
                                     );
-                                }
-
+                                } else {
                                     // prune zero_lamport_pubkey set which should contain all 0-lamport
                                     // keys whether rooted or not. A 0-lamport update may become rooted
                                     // in the future.
@@ -1581,6 +1580,7 @@ impl AccountsDb {
                                     if !has_zero_lamport_accounts {
                                         self.accounts_index.remove_zero_lamport_key(pubkey);
                                     }
+                                }
 
                                 // Release the lock
                                 let slot = *slot;