Added a way to get the spawn position of a world

worldedit-core/src/main/java/com/sk89q/worldedit/world/NullWorld.java

@@ -125,6 +125,11 @@ public class NullWorld extends AbstractWorld {
     public void setWeather(WeatherType weatherType, long duration) {
     }
 
+    @Override
+    public BlockVector3 getSpawnPosition() {
+        return BlockVector3.ZERO;
+    }
+
     @Override
     public BlockState getBlock(BlockVector3 position) {
         return BlockTypes.AIR.getDefaultState();