wesnothd: add a check to prevent crash from accessing game owner not …

…in player_connections_

(cherry-picked from commit 10ee2b2)

src/server/game.cpp

@@ -1528,7 +1528,11 @@ bool game::remove_player(const socket_ptr& player, const bool disconnect, const
 		// Check whether the host is actually a player and make him one if not.
 		if(!is_player(owner_)) {
 			DBG_GAME << "making the owner a player...\n";
-			player_connections_.find(owner_)->info().set_status(player::PLAYING);
+			auto owner_iter = player_connections_.find(owner_);
+			if(owner_iter == player_connections_.end())
+				ERR_GAME << "game owner " << client_address(owner_) << "is not in player_connections_\n";
+			else
+				owner_iter->info().set_status(player::PLAYING);
 			observers_.erase(std::remove(observers_.begin(), observers_.end(), owner_), observers_.end());
 			players_.push_back(owner_);
 			send_observerquit(owner_);