Runtime fix:  Sparks trying to delete that which does not exist.

runtime error: Cannot execute null.delete().
proc name: start (/datum/effect/effect/system/spark_spread/start)
  source file: effect_system.dm,204
  usr: Mark Hoover (/mob/living/carbon/human)
  src: /datum/effect/effect/system/sp... (/datum/effect/effect/system/spark_spread)
  call stack:
/datum/effect/effect/system/sp... (/datum/effect/effect/system/spark_spread): start()
runtime error: Cannot execute null.delete().
proc name: start (/datum/effect/effect/system/spark_spread/start)
  source file: effect_system.dm,204
  usr: Mark Hoover (/mob/living/carbon/human)
  src: /datum/effect/effect/system/sp... (/datum/effect/effect/system/spark_spread)
  call stack:
/datum/effect/effect/system/sp... (/datum/effect/effect/system/spark_spread): start()