Fix: commands with a RoadType in their arguments were not validated properly (#9944)

Although it was checked that RoadType was not 63 (INVALID_ROADTYPE),
and all values lower than 63 are fine, it also allowed values higher
than 63. As the RoadType is a "byte", it could contain values up
to 255.

src/road.cpp

@@ -141,7 +141,7 @@ bool HasAnyRoadTypesAvail(CompanyID company, RoadTramType rtt)
  */
 bool ValParamRoadType(RoadType roadtype)
 {
-	return roadtype != INVALID_ROADTYPE && HasRoadTypeAvail(_current_company, roadtype);
+	return roadtype < ROADTYPE_END && HasRoadTypeAvail(_current_company, roadtype);
 }
 
 /**