Fix crashes when joining a server in the Nether

core/src/main/java/org/geysermc/geyser/session/GeyserSession.java

@@ -1420,7 +1420,7 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         startGamePacket.setRotation(Vector2f.from(1, 1));
 
         startGamePacket.setSeed(-1L);
-        startGamePacket.setDimensionId(DimensionUtils.javaToBedrock(dimension));
+        startGamePacket.setDimensionId(DimensionUtils.javaToBedrock(chunkCache.getBedrockDimension()));
         startGamePacket.setGeneratorId(1);
         startGamePacket.setLevelGameType(GameType.SURVIVAL);
         startGamePacket.setDifficulty(1);

core/src/main/java/org/geysermc/geyser/translator/protocol/java/JavaLoginTranslator.java

@@ -99,6 +99,7 @@ public class JavaLoginTranslator extends PacketTranslator<ClientboundLoginPacket
         if (needsSpawnPacket) {
             // The player has yet to spawn so let's do that using some of the information in this Java packet
             session.setDimension(newDimension);
+            DimensionUtils.setBedrockDimension(session, newDimension);
             session.connect();
 
             // It is now safe to send these packets

core/src/main/java/org/geysermc/geyser/util/DimensionUtils.java

@@ -95,11 +95,7 @@ public class DimensionUtils {
         changeDimensionPacket.setPosition(pos);
         session.sendUpstreamPacket(changeDimensionPacket);
         session.setDimension(javaDimension);
-        session.getChunkCache().setBedrockDimension(switch (javaDimension) {
+        setBedrockDimension(session, javaDimension);
-            case DimensionUtils.THE_END -> BedrockDimension.THE_END;
-            case DimensionUtils.NETHER -> DimensionUtils.isCustomBedrockNetherId() ? BedrockDimension.THE_END : BedrockDimension.THE_NETHER;
-            default -> BedrockDimension.OVERWORLD;
-        });
         player.setPosition(pos);
         session.setSpawned(false);
         session.setLastChunkPosition(null);
@@ -137,6 +133,24 @@ public class DimensionUtils {
         }
     }
 
+    public static void setBedrockDimension(GeyserSession session, String javaDimension) {
+        session.getChunkCache().setBedrockDimension(switch (javaDimension) {
+            case DimensionUtils.THE_END -> BedrockDimension.THE_END;
+            case DimensionUtils.NETHER -> DimensionUtils.isCustomBedrockNetherId() ? BedrockDimension.THE_END : BedrockDimension.THE_NETHER;
+            default -> BedrockDimension.OVERWORLD;
+        });
+    }
+
+    public static int javaToBedrock(BedrockDimension dimension) {
+        if (dimension == BedrockDimension.THE_NETHER) {
+            return BEDROCK_NETHER_ID;
+        } else if (dimension == BedrockDimension.THE_END) {
+            return 2;
+        } else {
+            return 0;
+        }
+    }
+
     /**
      * Map the Java edition dimension IDs to Bedrock edition
      *