Fixes the switchblade letter opener and machete becoming invisible (#…

…3767)

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## About The Pull Request

switchblade now uses on/off sprite & has no world icon because it doesnt
have a world icon
letter opener now doesn't use world icons because it's stored in a
completely seperate file and doesn't have one either

machete now doesn't try to change its sprite on wielding because it
doesnt need to do that and also doesn't have the required sprite

## Why It's Good For The Game

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## Changelog

:cl:
fix: some weapons are now more visible than they weren't supposed to be
(which is none)
/:cl:

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code/game/objects/items/melee/knife.dm

@@ -161,6 +161,7 @@
 	icon_state = "switchblade"
 	lefthand_file = 'icons/mob/inhands/weapons/swords_lefthand.dmi'
 	righthand_file = 'icons/mob/inhands/weapons/swords_righthand.dmi'
+	world_file = null
 	desc = "A sharp, concealable, spring-loaded knife."
 	flags_1 = CONDUCT_1
 	force = 3
@@ -190,6 +191,7 @@
 /obj/item/melee/knife/letter_opener
 	name = "letter opener"
 	icon = 'icons/obj/items.dmi'
+	world_file = null
 	icon_state = "letter_opener"
 	desc = "A military combat utility survival knife."
 	embedding = list("pain_mult" = 4, "embed_chance" = 65, "fall_chance" = 10, "ignore_throwspeed_threshold" = TRUE)

code/game/objects/items/melee/sword.dm

@@ -67,7 +67,7 @@
 
 /obj/item/melee/sword/mass/ComponentInitialize()
 	. = ..()
-	AddComponent(/datum/component/two_handed, force_unwielded=20, force_wielded=22, icon_wielded="[base_icon_state]1")
+	AddComponent(/datum/component/two_handed, force_unwielded=20, force_wielded=22)
 
 /obj/item/melee/sword/katana
 	name = "katana"