fix battle table edge case

src/ReceiveCommands.cc

@@ -983,8 +983,10 @@ static bool start_ep3_battle_table_game_if_ready(
     if (c->card_battle_table_seat_number >= 4) {
       throw logic_error("invalid seat number");
     }
+    // Apparently this can actually happen; just prevent them from starting a
+    // battle if multiple players are in the same seat
     if (!table_clients.emplace(c->card_battle_table_seat_number, c).second) {
-      throw runtime_error("multiple clients in same battle table seat");
+      return false;
     }
     if (c->card_battle_table_seat_state == 3) {
       return false;

src/SendCommands.cc

@@ -1921,14 +1921,13 @@ void send_ep3_card_battle_table_state(shared_ptr<Lobby> l, uint16_t table_number
         throw runtime_error("invalid battle table seat number");
       }
       auto& e = cmd.entries[c->card_battle_table_seat_number];
-      if (e.state != 0) {
+      if (e.state == 0) {
-        throw runtime_error("multiple clients in the same battle table seat");
-      }
         e.state = c->card_battle_table_seat_state;
         e.guild_card_number = c->license->serial_number;
         clients.emplace(c);
       }
     }
+  }
 
   for (const auto& c : clients) {
     send_command_t(c, 0xE4, table_number, cmd);