Fix adding duplicate block states for custom blocks with 0 properties

Remove defaultBlockState CustomBlockState field from
GeyserCustomBlockData since it creates a circular reference

core/src/main/java/org/geysermc/geyser/level/block/GeyserCustomBlockData.java

@@ -49,8 +49,7 @@ public class GeyserCustomBlockData implements CustomBlockData {
     Map<String, CustomBlockProperty<?>> properties;
     List<CustomBlockPermutation> permutations;
 
-    @EqualsAndHashCode.Exclude // Otherwise this will a StackOverflowError in hashCode/equals
-    CustomBlockState defaultBlockState;
+    Map<String, Object> defaultProperties;
 
     private GeyserCustomBlockData(CustomBlockDataBuilder builder) {
         this.name = builder.name;
@@ -60,10 +59,9 @@ public class GeyserCustomBlockData implements CustomBlockData {
 
         this.components = builder.components;
 
-        Object2ObjectMap<String, Object> defaultProperties;
         if (!builder.properties.isEmpty()) {
             this.properties = Object2ObjectMaps.unmodifiable(new Object2ObjectArrayMap<>(builder.properties));
-            defaultProperties = new Object2ObjectOpenHashMap<>(this.properties.size());
+            Object2ObjectMap<String, Object> defaultProperties = new Object2ObjectOpenHashMap<>(this.properties.size());
             for (CustomBlockProperty<?> property : properties.values()) {
                 if (property.values().isEmpty() || property.values().size() > 16) {
                     throw new IllegalStateException(property.name() + " must contain 1 to 16 values.");
@@ -73,10 +71,10 @@ public class GeyserCustomBlockData implements CustomBlockData {
                 }
                 defaultProperties.put(property.name(), property.values().get(0));
             }
-            this.defaultBlockState = new GeyserCustomBlockState(this, Object2ObjectMaps.unmodifiable(defaultProperties));
+            this.defaultProperties = Object2ObjectMaps.unmodifiable(defaultProperties);
         } else {
             this.properties = Object2ObjectMaps.emptyMap();
-            this.defaultBlockState = new GeyserCustomBlockState(this, Object2ObjectMaps.emptyMap());
+            this.defaultProperties = Object2ObjectMaps.emptyMap();
         }
 
         if (!builder.permutations.isEmpty()) {
@@ -113,7 +111,7 @@ public class GeyserCustomBlockData implements CustomBlockData {
 
     @Override
     public @NonNull CustomBlockState defaultBlockState() {
-        return defaultBlockState;
+        return new GeyserCustomBlockState(this, defaultProperties);
     }
 
     @Override

core/src/main/java/org/geysermc/geyser/registry/populator/BlockRegistryPopulator.java

@@ -111,13 +111,6 @@ public class BlockRegistryPopulator {
     }
 
     private static void generateCustomBlockStates(CustomBlockData customBlock, List<NbtMap> blockStates, List<CustomBlockState> customExtBlockStates, int stateVersion) {
-        if (customBlock.properties().isEmpty()) {
-            blockStates.add(NbtMap.builder()
-                    .putString("name", customBlock.identifier())
-                    .putInt("version", stateVersion)
-                    .putCompound("states", NbtMap.EMPTY)
-                    .build());
-        }
         int totalPermutations = 1;
         for (CustomBlockProperty<?> property : customBlock.properties().values()) {
             totalPermutations *= property.values().size();