Removes non arrow-entities

[Lars Müller]

By looking at the code (https://bitbucket.org/minetest_gamers/x_bows/src/d57d5b0cf39f9e9843d5bfe31e451f0cc1babf73/arrow.lua#lines-439), I’m pretty sure this will delete non-arrow entities.

[Juraj Vajda]

Thanks, thats a good one. Should be resolved here: https://bitbucket.org/minetest_gamers/x_bows/pull-requests/5