Fix #12415, 9c49a61, df400ef: Aircraft::tile is valid only for front vehicle

[glx22]

Motivation / Problem

As per #12415, v->tile for aircraft shadow/rotor is always 0.

Description

Use tile from front part of the aircraft.

Limitations

Wondering if we should initialise Vehicle::tile to INVALID_TILE in Vehicle::Vehicle(VehicleType type).

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[rubidium42]

Initialising as invalid might indeed be a good idea. Potentially use a default member initializer, or maybe add the tile to the constructor so every vehicle needs to explicitly set it. Either way would be out of scope for this PR I'd say.