Failed to diagnose an NPE in 1.554.3.

WARNING: Caught exception evaluating: e.hasStopPermission() in /. Reason: java.lang.NullPointerException
java.lang.NullPointerException
	at hudson.model.Executor.hasStopPermission(Executor.java:523)

core/src/main/java/hudson/model/Queue.java

@@ -1278,14 +1278,13 @@ public class Queue extends ResourceController implements Saveable {
     public interface Executable extends Runnable {
         /**
          * Task from which this executable was created.
-         * Never null.
          *
          * <p>
          * Since this method went through a signature change in 1.377, the invocation may results in
          * {@link AbstractMethodError}.
          * Use {@link Executables#getParentOf(Queue.Executable)} that avoids this.
          */
-        SubTask getParent();
+        @Nonnull SubTask getParent();
 
         /**
          * Called by {@link Executor} to perform the task

core/src/main/java/hudson/model/queue/Executables.java

@@ -27,6 +27,7 @@ import hudson.model.Queue.Executable;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import javax.annotation.Nonnull;
 
 /**
  * Convenience methods around {@link Executable}.
@@ -37,7 +38,7 @@ public class Executables {
     /**
      * Due to the return type change in {@link Executable}, the caller needs a special precaution now.
      */
-    public static SubTask getParentOf(Executable e) {
+    public static @Nonnull SubTask getParentOf(Executable e) {
         try {
             return _getParentOf(e);
         } catch (AbstractMethodError _) {

core/src/main/java/hudson/model/queue/SubTask.java

@@ -29,8 +29,6 @@ import hudson.model.Node;
 import hudson.model.Queue.Executable;
 import hudson.model.Queue.Task;
 import hudson.model.ResourceActivity;
-import hudson.security.ACL;
-import org.acegisecurity.Authentication;
 
 import javax.annotation.Nonnull;
 import java.io.IOException;
@@ -78,7 +76,7 @@ public interface SubTask extends ResourceActivity {
     /**
      * Gets the {@link Task} that this subtask belongs to.
      */
-    Task getOwnerTask();
+    @Nonnull Task getOwnerTask();
 
     /**
      * If a subset of {@link SubTask}s of a {@link Task} needs to be collocated with other {@link SubTask}s,

core/src/main/java/hudson/model/queue/Tasks.java

@@ -81,7 +81,7 @@ public class Tasks {
         return t.getOwnerTask();
     }
 
-    public static Task getOwnerTaskOf(SubTask t) {
+    public static @Nonnull Task getOwnerTaskOf(@Nonnull SubTask t) {
         try {
             return _getOwnerTaskOf(t);
         } catch (AbstractMethodError e) {