getExecutionStacks returns NotNull

platform/xdebugger-api/src/com/intellij/xdebugger/frame/XSuspendContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * Copyright 2000-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,6 +37,7 @@ public abstract class XSuspendContext {
     return null;
   }
 
+  @NotNull
   public XExecutionStack[] getExecutionStacks() {
     XExecutionStack executionStack = getActiveExecutionStack();
     return executionStack != null ? new XExecutionStack[]{executionStack} : XExecutionStack.EMPTY_ARRAY;

plugins/xslt-debugger/src/org/intellij/plugins/xsltDebugger/impl/XsltDebugProcess.java

@@ -196,6 +196,7 @@ public class XsltDebugProcess extends XDebugProcess implements Disposable {
       return new XsltExecutionStack("Source Frames", mySourceFrame, myDebuggerSession);
     }
 
+    @NotNull
     @Override
     public XExecutionStack[] getExecutionStacks() {
       return new XExecutionStack[]{

python/src/com/jetbrains/python/debugger/PySuspendContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * Copyright 2000-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,6 +37,7 @@ public class PySuspendContext extends XSuspendContext {
     return myActiveStack;
   }
 
+  @NotNull
   @Override
   public XExecutionStack[] getExecutionStacks() {
     final Collection<PyThreadInfo> threads = myDebugProcess.getThreads();