Fix: Deleting towns did not check for waypoints referencing the town

src/town_cmd.cpp

@@ -17,6 +17,7 @@
 #include "command_func.h"
 #include "industry.h"
 #include "station_base.h"
+#include "waypoint_base.h"
 #include "station_kdtree.h"
 #include "company_base.h"
 #include "news_func.h"
@@ -3040,6 +3041,11 @@ CommandCost CmdDeleteTown(DoCommandFlag flags, TownID town_id)
 		}
 	}
 
+	/* Waypoints refer to towns. */
+	for (const Waypoint *wp : Waypoint::Iterate()) {
+		if (wp->town == t) return CMD_ERROR;
+	}
+
 	/* Depots refer to towns. */
 	for (const Depot *d : Depot::Iterate()) {
 		if (d->town == t) return CMD_ERROR;