Chunnel: Adjust struct Tunnel constructor

src/saveload/afterload.cpp

@@ -2040,9 +2040,7 @@ bool AfterLoadGame()
 
 					if (!Tunnel::CanAllocateItem()) return false;
 
-					Tunnel *t = new Tunnel(start_tile);
-					t->tile_s = end_tile;
-					t->is_chunnel = 0;
+					const Tunnel *t = new Tunnel(start_tile, end_tile, false);
 
 					_m[start_tile].m2 = t->index;
 					_m[end_tile].m2 = t->index;

src/tunnel_base.h

@@ -26,7 +26,8 @@ struct Tunnel : TunnelPool::PoolItem<&_tunnel_pool> {
 	TileIndex tile_s; // South tile of tunnel.
 	bool is_chunnel;
 
-	Tunnel(TileIndex tile_n = INVALID_TILE) : tile_n(tile_n) {}
+	Tunnel() {}
+	Tunnel(TileIndex tile_n, TileIndex tile_s, bool is_chunnel) : tile_n(tile_n), tile_s(tile_s), is_chunnel(is_chunnel) {}
 	~Tunnel();
 
 	static inline Tunnel *GetByTile(TileIndex tile)

src/tunnelbridge_cmd.cpp

@@ -814,9 +814,7 @@ CommandCost CmdBuildTunnel(TileIndex start_tile, DoCommandFlag flags, uint32 p1,
 		if(start_tile > end_tile) Swap(tn, ts);
 
 		if (!Tunnel::CanAllocateItem()) return CMD_ERROR;
-		Tunnel *t = new Tunnel(tn);
-		t->tile_s = ts;
-		t->is_chunnel = is_chunnel;
+		const Tunnel *t = new Tunnel(tn, ts, is_chunnel);
 
 		if (transport_type == TRANSPORT_RAIL) {
 			if (!IsTunnelTile(start_tile) && c != NULL) c->infrastructure.rail[railtype] += num_pieces;