some of negative xml tests are fails with NPE instead of fail with other exceptions

jdk6.0-b46: some of negative xml tests are fails with NPE instead of fail with other exceptions:

api/javax_xml/xmlCore/w3c/ibm/ibm_not_wf.html#ibm_not_wf_P09_ibm09n04_xml open quote should have corresponding close quote, but NPE thrown
api/javax_xml/xmlCore/w3c/ibm/ibm_not_wf.html#ibm_not_wf_P29_ibm29n06_xml NPE unclosed comment in xml text, but NPE thrown
api/javax_xml/xmlCore/w3c/oasis/oasis.html#o_p09fail4 NPE quotes type should match, but NPE thrown
api/javax_xml/xmlCore/w3c/oasis/oasis.html#o_p09fail5 NPE quotes type should match, but NPE thrown
api/javax_xml/xmlCore/w3c/oasis/oasis.html#o_p11fail1 NPE quotes type should match, but NPE thrown
api/javax_xml/xmlCore/w3c/xmltest/xmltest_not_wf.html#not_wf_sa_179 incorrect matching quote JDK but Null pointer thrown

Possible reason of these fails in changes been implemented in com.sun.org.apache.xerces.internal.impl.* classes in mustang build 46.
JCK: 6.0 b04