Problem: If AI drives through a fill trigger it will fill attached implement

Expected behavior: AI drives through a fill trigger and nothing is added to attached implement

Steps to reproduce:
1) Buy tractor and fertilizer spreader, attach fertilizer spreader tractor
2) Buy small amount of fertilizer, such that tank is not full
3) Position tractor close to fill trigger (Co-op for example)
4) Create map navigation point such that tractor will drive through the fill trigger
5) Press N to activate autopilot

Note this also happens if the fertilizer spreader tank is empty but has a filltype assigned (i.e. it has been filled in the past but is now empty)