tweak ItemStack names

mappings/net/minecraft/item/Item.mapping

@@ -81,6 +81,7 @@ CLASS avi net/minecraft/item/Item
 	METHOD a getItemFromBlock (Lbfo;)Lavi;
 		ARG 0 block
 	METHOD a isEffectiveOn (Lboh;)Z
+	METHOD a beforeBlockBreak (Lboh;Lbam;Les;Laqf;)Z
 	METHOD a onTagDeserialized (Lho;)Z
 	METHOD a getProperty (Lpx;)Lavm;
 	METHOD a addProperty (Lpx;Lavm;)V

mappings/net/minecraft/item/ItemDebugStick.mapping

@@ -1,3 +1,4 @@
 CLASS aug net/minecraft/item/ItemDebugStick
 	METHOD a useOnBlock (Laxa;)Laez;
+	METHOD a beforeBlockBreak (Lboh;Lbam;Les;Laqf;)Z
 	METHOD e_ hasEnchantmentGlow (Lavn;)Z

mappings/net/minecraft/item/ItemStack.mapping

@@ -1,5 +1,5 @@
 CLASS avn net/minecraft/item/ItemStack
-	FIELD a NULL_STACK Lavn;
+	FIELD a AIR Lavn;
 	FIELD b MODIFIER_FORMAT Ljava/text/DecimalFormat;
 	FIELD c LOGGER Lorg/apache/logging/log4j/Logger;
 	FIELD d amount I
@@ -14,14 +14,16 @@ CLASS avn net/minecraft/item/ItemStack
 	FIELD m lastCheckedCanPlaceResult Z
 	METHOD <init> (Lbal;I)V
 		ARG 1 container
+		ARG 2 amount
 	METHOD A getRepairCost ()I
 	METHOD B toTextComponent ()Liz;
 	METHOD C getUpdateCooldown ()I
 	METHOD D getAmount ()I
 	METHOD E createModifierFormat ()Ljava/text/DecimalFormat;
-	METHOD F updateInvalidFlag ()V
-	METHOD a isInvalid ()Z
+	METHOD F updateEmptyFlag ()V
+	METHOD a isEmpty ()Z
 	METHOD a split (I)Lavn;
+		ARG 1 amount
 	METHOD a applyDamage (ILagn;)V
 	METHOD a applyDamage (ILjava/util/Random;Lui;)Z
 		ARG 1 amount
@@ -92,7 +94,7 @@ CLASS avn net/minecraft/item/ItemStack
 		ARG 1 b
 	METHOD c setTag (Lho;)V
 	METHOD c removeSubTag (Ljava/lang/String;)V
-	METHOD d canBeStacked ()Z
+	METHOD d canStack ()Z
 	METHOD d setUpdateCooldown (I)V
 	METHOD d areEqualIgnoreDurability (Lavn;Lavn;)Z
 		ARG 0 a

mappings/net/minecraft/item/ItemSword.mapping

@@ -12,3 +12,4 @@ CLASS aws net/minecraft/item/ItemSword
 	METHOD a getBlockBreakingSpeed (Lavn;Lboh;)F
 		ARG 1 stack
 	METHOD a isEffectiveOn (Lboh;)Z
+	METHOD a beforeBlockBreak (Lboh;Lbam;Les;Laqf;)Z

mappings/net/minecraft/item/ItemTrident.mapping

@@ -15,6 +15,7 @@ CLASS awy net/minecraft/item/ItemTrident
 	METHOD a use (Lbam;Laqf;Laex;)Lafa;
 		ARG 1 world
 		ARG 2 player
+	METHOD a beforeBlockBreak (Lboh;Lbam;Les;Laqf;)Z
 	METHOD b getMaxUseTime (Lavn;)I
 	METHOD c getEnchantability ()I
 	METHOD c getUseAction (Lavn;)Lawz;