Bukkit/CraftBukkit — pull request #674 by steffengy (2012-02-19 11:01:49+00:00)
Title: Fixed behavior of ignited Arrows 

Now its like this:
PVP is disabled, you shoot an arrow, hit an sheep, it isn't burned.

This behavior is fixed in this, now it is checked if the destination is a Player, if not it gets burned.