After closing a DataSet, an attempt to close the associated Query object throws a NPE, even though the isClosed() method of the Query object returns false.

The attached test case produces the following output:

Dropping table...
Creating table...
Closing DataSet addressesDS.
Is addressesDS closed? true
Is Query object aq closed? false
Closing Query object aq.
Exception in thread "main" java.sql.SQLRuntimeException: java.lang.NullPointerException
        at com.sun.sql.QueryObjectGeneratorImpl.deregisterAllDataSets(Unknown Source)
        at com.sun.sql.QueryObjectGeneratorImpl.invoke(Unknown Source)
        at $Proxy0.close(Unknown Source)
        at CloseTest.main(CloseTest.java:67)
Caused by: java.lang.NullPointerException
        at com.sun.sql.DataSetImpl$DataSetItr.<init>(Unknown Source)
        at com.sun.sql.DataSetImpl.iterator(Unknown Source)
        at java.util.AbstractList.hashCode(AbstractList.java:524)
        at java.util.WeakHashMap.remove(WeakHashMap.java:543)
        at java.util.WeakHashMap$HashIterator.remove(WeakHashMap.java:779)
        ... 4 more