Added a few null checks.

code/modules/organs/organ_external.dm

@@ -3,13 +3,16 @@
 ****************************************************/
 /obj/item/organ/external
 	name = "external"
+	min_broken_damage = 30
+	max_damage = 0
+	dir = SOUTH
+	organ_tag = "limb"
+
 	var/icon_name = null
 	var/body_part = null
 	var/icon_position = 0
-
 	var/model
 	var/force_icon
-
 	var/damage_state = "00"
 	var/brute_dam = 0
 	var/burn_dam = 0
@@ -26,38 +29,25 @@
 	var/list/wounds = list()
 	var/number_wounds = 0 // cache the number of wounds, which is NOT wounds.len!
 	var/perma_injury = 0
-
 	var/obj/item/organ/external/parent
 	var/list/obj/item/organ/external/children
-
-	// Internal organs of this body part
-	var/list/internal_organs = list()
-
+	var/list/internal_organs = list() 	// Internal organs of this body part
 	var/damage_msg = "\red You feel an intense pain"
 	var/broken_description
-
 	var/open = 0
 	var/stage = 0
 	var/cavity = 0
 	var/sabotaged = 0 // If a prosthetic limb is emagged, it will detonate when it fails.
 	var/encased       // Needs to be opened with a saw to access the organs.
-
 	var/obj/item/hidden = null
 	var/list/implants = list()
-
-	// how often wounds should be updated, a higher number means less often
-	var/wound_update_accuracy = 1
-
+	var/wound_update_accuracy = 1 	// how often wounds should be updated, a higher number means less often
 	var/joint = "joint"   // Descriptive string used in dislocation.
 	var/amputation_point  // Descriptive string used in amputation.
 	var/dislocated = 0    // If you target a joint, you can dislocate the limb, causing temporary damage to the organ.
 	var/can_grasp
 	var/can_stand
 
-	min_broken_damage = 30
-	max_damage = 0
-	dir = SOUTH
-
 /obj/item/organ/external/attackby(obj/item/weapon/W as obj, mob/user as mob)
 	switch(stage)
 		if(0)