Try this version, otherwise maybe downgrade?

src/main/java/com/plotsquared/bukkit/util/BukkitUtil.java

@@ -146,8 +146,10 @@ public class BukkitUtil extends BlockManager {
 
     public static World getWorld(final String string) {
         if (StringMan.isEqual(string, lastString)) {
+            if (lastWorld != null) {
                 return lastWorld;
             }
+        }
         World world = Bukkit.getWorld(string);
         lastString = string;
         lastWorld = world;