[ci skip] Add nullable annotation to field (#7042)

Co-authored-by: Riley Park <riley.park@meino.net>

Author: Owen1212055

patches/server/0242-Add-Debug-Entities-option-to-debug-dupe-uuid-issues.patch

@@ -79,7 +79,7 @@ index 2a11514554b6aea819046282cfcaeeb43d1ed920..2981a29b011cb1a08a776abc5ec6a942
      public com.destroystokyo.paper.loottable.PaperLootableInventoryData lootableData; // Paper
      private CraftEntity bukkitEntity;
 
-+    public net.minecraft.server.level.ChunkMap.TrackedEntity tracker; // Paper
++    public @org.jetbrains.annotations.Nullable net.minecraft.server.level.ChunkMap.TrackedEntity tracker; // Paper
 +    public Throwable addedToWorldStack; // Paper - entity debug
      public CraftEntity getBukkitEntity() {
          if (this.bukkitEntity == null) {

patches/server/0393-Optimize-Collision-to-not-load-chunks.patch

@@ -26,7 +26,7 @@ index 81aee8c195307fd3cd4a89c29ebb7ebc25436c83..2458619f7f377398322459e00a49f7f4
              entityplayer1.setPos(entityplayer1.getX(), entityplayer1.getY() + 1.0D, entityplayer1.getZ());
          }
 diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
-index 497fec66a9bb22ca9e4c8eea6c588bb42f64b320..fa4242cb9bd5b8b5a088585a6709d0b27835a261 100644
+index bd45dea99ea38b07577e2dbf399b87856bc28573..333686cdcedd612ddbd33ec0ef8a3beb326d41b3 100644
 --- a/src/main/java/net/minecraft/world/entity/Entity.java
 +++ b/src/main/java/net/minecraft/world/entity/Entity.java
 @@ -171,6 +171,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, i
@@ -36,7 +36,7 @@ index 497fec66a9bb22ca9e4c8eea6c588bb42f64b320..fa4242cb9bd5b8b5a088585a6709d0b2
 +    public boolean collisionLoadChunks = false; // Paper
      private CraftEntity bukkitEntity;
 
-     public net.minecraft.server.level.ChunkMap.TrackedEntity tracker; // Paper
+     public @org.jetbrains.annotations.Nullable net.minecraft.server.level.ChunkMap.TrackedEntity tracker; // Paper
 diff --git a/src/main/java/net/minecraft/world/level/BlockCollisions.java b/src/main/java/net/minecraft/world/level/BlockCollisions.java
 index 8390ce194ccc692139c0e870c16a7fb76ac8ba68..a733c91700a38634806e9155c693b227e6aa16b6 100644
 --- a/src/main/java/net/minecraft/world/level/BlockCollisions.java