bug fix

src/main/java/pers/xanadu/enderdragon/manager/DragonManager.java

@@ -490,7 +490,8 @@ public class DragonManager {
      */
     public static EnderDragon getEnderDragon(final World world){
         if(world.getEnvironment() != World.Environment.THE_END){
-            return world.getEntitiesByClass(EnderDragon.class).iterator().next();
+            Iterator<EnderDragon> iterator = world.getEntitiesByClass(EnderDragon.class).iterator();
+            return iterator.hasNext()?iterator.next():null;
         }
         if(Version.mcMainVersion >= 16){
             DragonBattle battle = world.getEnderDragonBattle();

src/main/resources/plugin.yml

@@ -1,5 +1,5 @@
 name: EnderDragon
-version: 2.5.0
+version: 2.5.1
 main: pers.xanadu.enderdragon.EnderDragon
 author: Xanadu13
 api-version: 1.13