Fix ChunkHolder#getFullChunkNow returning non-null when it should not

In the new chunk system, the chunk is only at FULL when either
the FULL callbacks have been invoked or during the FULL callbacks.

patches/server/0991-Chunk-System-Starlight-from-Moonrise.patch

@@ -22722,7 +22722,7 @@ index e14c0e1ccf526f81e28db5545d9e2351641e1bc8..3c230ae060998bfb79d5812fef21a80a
      public boolean isDebugging() {
          return false;
 diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
-index c643bb0daa5cd264fd6ebab7acf0a2bdd7fe7029..0048077dedd19adc6c5a88e7d916d88a71662115 100644
+index c643bb0daa5cd264fd6ebab7acf0a2bdd7fe7029..9bc59697fc71d4e3c226aa7fe958f57193fc4bd4 100644
 --- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
 +++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
 @@ -32,28 +32,20 @@ import net.minecraft.world.level.lighting.LevelLightEngine;
@@ -22899,7 +22899,7 @@ index c643bb0daa5cd264fd6ebab7acf0a2bdd7fe7029..0048077dedd19adc6c5a88e7d916d88a
      public LevelChunk getFullChunkNow() {
          // Note: We use the oldTicketLevel for isLoaded checks.
 -        if (!ChunkLevel.fullStatus(this.oldTicketLevel).isOrAfter(FullChunkStatus.FULL)) return null;
-+        if (!ChunkLevel.fullStatus(this.newChunkHolder.oldTicketLevel).isOrAfter(FullChunkStatus.FULL)) return null; // Paper - rewrite chunk system
++        if (!this.newChunkHolder.isFullChunkReady()) return null; // Paper - rewrite chunk system
          return this.getFullChunkNowUnchecked();
      }