Fix #3806: Other Coaster Vehicle options not showing in Ride Window

This error was introduced with aa929e1 (see line 204 in src/management/research.c in that commit).

src/management/research.c

@@ -203,7 +203,7 @@ void research_finish_item(sint32 entryIndex)
 					rideEntry2->ride_type[1] == base_ride_type ||
 					rideEntry2->ride_type[2] == base_ride_type
 				) {
-					ride_entry_set_invented(rideEntryIndex);
+					ride_entry_set_invented(i);
 				}
 			}
 		}