Updated Upstream (Bukkit/CraftBukkit/Spigot)

Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Please note that this build includes changes to meet upstreams
requirements for nullability annotations. While we aim for a level of
accuracy, these might not be 100% correct, if there are any issues,
please speak to us on discord, or open an issue on the tracker to
discuss.

Bukkit Changes:
9a6a1de3 Remove nullability annotations from enum constructors
3f0591ea SPIGOT-2540: Add nullability annotations to entire Bukkit API

CraftBukkit Changes:
8d8475fc SPIGOT-4666: Force parameter in HumanEntity#sleep
8b1588e2 Fix ExplosionPrimeEvent#setFire not working with EnderCrystals
39a287b7 Don't ignore newlines in PlayerListHeader/Footer

Spigot Changes:
cf694d87 Add nullability annotations

Spigot-API-Patches/PlayerReadyArrowEvent.patch

@@ -8,7 +8,7 @@ Plugins can skip selection of certain arrows and control which is used.
 
 diff --git a/src/main/java/com/destroystokyo/paper/event/player/PlayerReadyArrowEvent.java b/src/main/java/com/destroystokyo/paper/event/player/PlayerReadyArrowEvent.java
 new file mode 100644
-index 00000000..6fde1e97
+index 000000000..5d04a22fd
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/event/player/PlayerReadyArrowEvent.java
 @@ -0,0 +0,0 @@
@@ -43,15 +43,16 @@ index 00000000..6fde1e97
 +import org.bukkit.event.HandlerList;
 +import org.bukkit.event.player.PlayerEvent;
 +import org.bukkit.inventory.ItemStack;
++import org.jetbrains.annotations.NotNull;
 +
 +/**
 + * Called when a player is firing a bow and the server is choosing an arrow to use.
 + */
 +public class PlayerReadyArrowEvent extends PlayerEvent implements Cancellable {
-+    private final ItemStack bow;
-+    private final ItemStack arrow;
++    @NotNull private final ItemStack bow;
++    @NotNull private final ItemStack arrow;
 +
-+    public PlayerReadyArrowEvent(Player player, ItemStack bow, ItemStack arrow) {
++    public PlayerReadyArrowEvent(@NotNull Player player, @NotNull ItemStack bow, @NotNull ItemStack arrow) {
 +        super(player);
 +        this.bow = bow;
 +        this.arrow = arrow;
@@ -60,6 +61,7 @@ index 00000000..6fde1e97
 +    /**
 +     * @return the player is using to fire the arrow
 +     */
++    @NotNull
 +    public ItemStack getBow() {
 +        return bow;
 +    }
@@ -67,16 +69,19 @@ index 00000000..6fde1e97
 +    /**
 +     * @return the arrow that is attempting to be used
 +     */
++    @NotNull
 +    public ItemStack getArrow() {
 +        return arrow;
 +    }
 +
 +    private static final HandlerList handlers = new HandlerList();
 +
++    @NotNull
 +    public HandlerList getHandlers() {
 +        return handlers;
 +    }
 +
++    @NotNull
 +    public static HandlerList getHandlerList() {
 +        return handlers;
 +    }