Exception stack trace is printed to console when Harness starts

When JavaTest Harness starts, NullPointerException is printed to console sometimes. It happens if work directory is specified in a command line that was used by some other test suite. There is my command line and the stack trace:

$ java -jar lib/javatest.jar -testsuite . -workdir /home/dl156063/tmp/workdir030

Error getting configuration: cannot initialize configuration: Cannot open work directory /home/dl156063/tmp/workdir030.
Work directory does not match the specified test suite.
java.lang.NullPointerException
at com.sun.javatest.exec.ExecToolManager.startTool(ExecToolManager.java:398)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.javatest.tool.Desktop.addDefaultTool(Desktop.java:383)
at com.sun.javatest.tool.Main$4.run(Main.java:431)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:199)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)