Animation for Rocket-explosion not on impact

[HaJo]

I noticed the animation of the rocket-explosion is shown at the wrong place,
i.e. 2-3 squares away from the point of impact.
Looking more closely, there is a small fireball at the place of impact,
but the big fireball is misplaced 2-3 squares.

See screenshots on issue 1537110 "Rocket-explosion not on impact" on sf.net,
https://sourceforge.net/tracker/index.php?func=detail&aid=1537110&group_id=157793&atid=805242