fixed run error

src/pocketmine/Server.php

@@ -60,7 +60,7 @@ use pocketmine\level\generator\Generator;
 use pocketmine\level\generator\hell\Nether;
 use pocketmine\level\generator\normal\Normal;
 use pocketmine\level\generator\normal\Normal2;
-use pocketmine\level\generator\Void;
+use pocketmine\level\generator\VoidGenerator;
 use pocketmine\level\Level;
 use pocketmine\level\LevelException;
 use pocketmine\metadata\EntityMetadataStore;
@@ -1913,7 +1913,7 @@ class Server{
 			Generator::addGenerator(Normal::class, "default");
 			Generator::addGenerator(Nether::class, "hell");
 			Generator::addGenerator(Nether::class, "nether");
-			Generator::addGenerator(Void::class, "void");
+			Generator::addGenerator(VoidGenerator::class, "void");
 			Generator::addGenerator(Normal2::class, "normal2");
 			Generator::addGenerator(Ender::class, "ender");
 

src/pocketmine/level/generator/Void.php

@@ -27,7 +27,7 @@ use pocketmine\level\format\Chunk;
 use pocketmine\math\Vector3;
 use pocketmine\utils\Random;
 
-class Void extends Generator {
+class VoidGenerator extends Generator {
 	/** @var ChunkManager */
 	private $level;
 	/** @var Chunk */