Pod Seeking Weaponry [Feature]

In the 2016 release, lines 344 and 345 of projectile_parent.dm don't account for the possibility of xo or yo actually being zero. This means that do_step will oftentimes cause a division by zero error runtime when using rotateDirection.
Example:

Code:
runtime error: Division by zero

proc name: do step (/obj/projectile/proc/do_step)

  source file: projectile_parent.dm,344

  usr: the buttface mcgee (as Osbert ... (/mob/living/carbon/human)

  src: the projectile (/obj/projectile)

  usr.loc: the floor (173,148,1) (/turf/simulated/floor)

  src.loc: null

  call stack:

the projectile (/obj/projectile): do step()

the projectile (/obj/projectile): process()

the projectile (/obj/projectile): launch()