fixes blackbox runtime and adds note about nested tally strings

code/controllers/subsystem/blackbox.dm

@@ -154,6 +154,7 @@ feedback data can be recorded in 5 formats:
 	used to track the number of occurances of structured semi-relational values i.e. the results of arcade machines
 	similar to running total, but related values are nested in a multi-dimensional array built
 	the final element in the data list is used as the tracking key, all prior elements are used for nesting
+	all data list elements must be strings
 	further calls to the same key will:
 	 	add or subtract from the saved value of the data key if it already exists in the same multi-dimensional position
 		append the key and it's value if it doesn't exist

code/modules/mob/living/carbon/human/human_defense.dm

@@ -162,7 +162,7 @@
 		affecting = get_bodypart(ran_zone(user.zone_selected))
 	var/target_area = parse_zone(check_zone(user.zone_selected)) //our intended target
 
-	SSblackbox.record_feedback("nested tally", "item_used_for_combat", 1, list(I.force, I.type))
+	SSblackbox.record_feedback("nested tally", "item_used_for_combat", 1, list("[I.force]", "[I.type]"))
 	SSblackbox.record_feedback("tally", "zone_targeted", 1, target_area)
 
 	// the attacked_by code varies among species