Fix isCurrentlyRunning for sync tasks

Not sure where this would of ever been used, but for correctness sake.

Spigot-Server-Patches/Improved-Async-Task-Scheduler.patch

@@ -204,7 +204,7 @@ index 000000000..cf5aada2f
 +    }
 +}
 diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
-index e47f4cca2..4a4159879 100644
+index e47f4cca2..c3cb9e6d2 100644
 --- a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
 +++ b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
 @@ -0,0 +0,0 @@ import java.util.concurrent.atomic.AtomicReference;
@@ -311,8 +311,10 @@ index e47f4cca2..4a4159879 100644
  
      public boolean isCurrentlyRunning(final int taskId) {
 +        // Paper start
-+        if (!isAsyncScheduler) { //noinspection TailRecursion
-+            return this.asyncScheduler.isCurrentlyRunning(taskId);
++        if (!isAsyncScheduler) {
++            if (this.asyncScheduler.isCurrentlyRunning(taskId)) {
++                return true;
++            }
 +        }
 +        // Paper end
          final CraftTask task = runners.get(taskId);