Fix possible error

api/src/main/java/net/momirealms/customcrops/api/core/world/WorldScheduler.java

@@ -51,6 +51,7 @@ public class WorldScheduler {
             thread.setName("customcrops-world-scheduler");
             return thread;
         });
+        this.scheduler.setMaximumPoolSize(1);
         this.scheduler.setRemoveOnCancelPolicy(true);
         this.scheduler.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
         this.worker = new ForkJoinPool(PARALLELISM, new WorkerThreadFactory(), new ExceptionHandler(), false);

api/src/main/java/net/momirealms/customcrops/api/core/world/adaptor/AbstractWorldAdaptor.java

@@ -128,6 +128,7 @@ public abstract class AbstractWorldAdaptor<W> implements WorldAdaptor<W> {
     }
 
     private int[] queueToIntArray(PriorityQueue<DelayedTickTask> queue) {
+        queue.removeIf(Objects::isNull);
         int size = queue.size() * 2;
         int[] tasks = new int[size];
         int i = 0;