skygrid-height: 256 causes empty chests, default spawners, and no errors.

[alentoghostflame]

Description
Setting skygrid-height to 256 causes all spawners to stay the default (pig) and all chests to be empty, without any errors in console.

Steps to reproduce the behavior:

1. In plugins/BentoBox/addons/SkyGrid/config.yml change skygrid-height: 128 to skygrid-height: 256.
2. Start up server to generate worlds.
3. Create an island and check chests/spawners.

Expected behavior
Either:
A. An error is thrown in console and the server shuts down.
B. An error is thrown in console and the plugin rounds the skygrid-height to a working value.
C. No error is thrown in console, and the plugin rounds the skygrid-height to a working value.

Screenshots
If applicable, add screenshots to help explain your problem.

Server Information:
[Please complete the following information:]

• Database being used (YAML, JSON, MySQL, MongoDB): JSON
• OS: Ubuntu 19.10 with Linux Kernel 5.5.4
• Java Version: OpenJDK 11.0.6 2020-01-14 (This comes bundled with the Linux Minecraft.deb installer)
• BentoBox version: 1.11.1
• Addons installed? [Do '/bentobox version' and copy/paste from the console]

[14:52:58] [Server thread/INFO]: Loaded Game Worlds:
[14:52:58] [Server thread/INFO]: skygrid-world (SkyGrid): Overworld, Nether, The End
[14:52:58] [Server thread/INFO]: Loaded Addons:
[14:52:58] [Server thread/INFO]: Biomes 1.6.0.1 (ENABLED)
[14:52:58] [Server thread/INFO]: Challenges 0.8.0 (ENABLED)
[14:52:58] [Server thread/INFO]: Chat 1.0.4 (ENABLED)
[14:52:58] [Server thread/INFO]: ControlPanel 1.7.0 (ENABLED)
[14:52:58] [Server thread/INFO]: DimensionalTrees 1.6.0 (ENABLED)
[14:52:58] [Server thread/INFO]: ExtraMobs 1.11.0.2 (ENABLED)
[14:52:58] [Server thread/INFO]: Greenhouses 1.0.0 (ENABLED)
[14:52:58] [Server thread/INFO]: Level 1.9.3 (ENABLED)
[14:52:58] [Server thread/INFO]: Likes 1.7.0 (ENABLED)
[14:52:58] [Server thread/INFO]: MagicCobblestoneGenerator 1.7.0.2 (ENABLED)
[14:52:58] [Server thread/INFO]: MagicSummon 1.5.0.0 (ENABLED)
[14:52:58] [Server thread/INFO]: SkyGrid 1.11.0 (ENABLED)
[14:52:58] [Server thread/INFO]: TwerkingForTrees 1.1.2 (ENABLED)
[14:52:58] [Server thread/INFO]: Warps 1.9.0 (ENABLED)

• Other plugins? [Do '/plugins' and copy/paste from the console]
  SimpleTpa, WorldEdit, EasySetSpawn, VoidGenerator, BentoBox, VoidSpawn, WorldGuard
  Additional context
  Not much. Setting skygrid-height to 253 causes everything to work fine.

[BONNe]

I assume because world height cannot be larger than 255?
However, bentobox should handle it.

Why 255 if world height is 256 blocks? Because in Java everything always starts from 0 :D