Skip registering "custom" biome.

Update adapters to 332c1f6bb17d2ded53fe5b09f3f2a4578f3f9bfc

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/WorldEditPlugin.java

@@ -320,6 +320,10 @@ public class WorldEditPlugin extends JavaPlugin {
         } else {
             LOGGER.warn("Failed to load biomes via adapter (not present). Will load via bukkit");
             for (Biome biome : Biome.values()) {
+                // Custom is bad
+                if (biome == Biome.CUSTOM) {
+                    continue;
+                }
                 String lowerCaseBiome = biome.getKey().toString().toLowerCase(Locale.ROOT);
                 // only register once
                 if (BiomeType.REGISTRY.get(lowerCaseBiome) == null) {