Bug

[thinh2118]

• Issue Description: [23:51:51] [Asynchronous Worker přidej češtinu #3 thread/CRITICAL]: TypeError: "Return value of pocketmine\level\biome\Biome::getMinElevation() must be of the type int, null returned" (EXCEPTION) in "pmsrc/src/pocketmine/level/biome/Biome" at line 165
  [23:51:51] [Asynchronous Worker přidej češtinu #3 thread/CRITICAL]: #0 plugins/MultiWorld.phar/src/czechpmdevs/multiworld/generator/normal/NormalGenerator(188): pocketmine\level\biome\Biome->getMinElevation()
  [23:51:51] [Asynchronous Worker přidej češtinu #3 thread/CRITICAL]: Feature #1 pmsrc/src/pocketmine/level/generator/PopulationTask(108): czechpmdevs\multiworld\generator\normal\NormalGenerator->generateChunk(integer 56, integer 7)
  [23:51:51] [Asynchronous Worker přidej češtinu #3 thread/CRITICAL]: Feature request: add world editor #2 pmsrc/src/pocketmine/scheduler/AsyncTask(85): pocketmine\level\generator\PopulationTask->onRun()
  [23:51:51] [Asynchronous Worker přidej češtinu #3 thread/CRITICAL]: přidej češtinu #3 (): pocketmine\scheduler\AsyncTask->run()
  [23:51:52] [Server thread/CRITICAL]: Could not execute asynchronous task PopulationTask: Task crashed

• Version: 1.5.2

• Server Version: 1.16.201

• Crashdump, backtrace or other files: