added NotNull

java/debugger/impl/src/com/intellij/debugger/jdi/ThreadReferenceProxyImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2016 JetBrains s.r.o.
+ * Copyright 2000-2017 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.
@@ -207,6 +207,7 @@ public final class ThreadReferenceProxyImpl extends ObjectReferenceProxyImpl imp
     return myFrameCount;
   }
 
+  @NotNull
   public List<StackFrameProxyImpl> frames() throws EvaluateException {
     DebuggerManagerThreadImpl.assertIsManagerThread();
     final ThreadReference threadRef = getThreadReference();