Crash the generator when encountering invalid presets

this is a partial fix for #2717, but still not ideal because it'll spam whenever a chunk is attempted to be generated. However, fixing this properly requires potentially breaking API changes.

src/pocketmine/level/generator/Generator.php

@@ -58,6 +58,11 @@ abstract class Generator{
 	/** @var Random */
 	protected $random;
 
+	/**
+	 * @param array $settings
+	 *
+	 * @throws InvalidGeneratorOptionsException
+	 */
 	abstract public function __construct(array $settings = []);