Null pointer exception because of unknown simple type

[ghost]

it seems that the parser doesn't add simple types so they cannot be refereneced later from complex types, examples from lom.xsd

 <xs:simpleType name="t_CharacterString">
    <xs:restriction base="xs:string"/>
  </xs:simpleType>
  <!-- LanguageId -->
  <xs:simpleType name="t_LanguageIdOrNone">
    <xs:union memberTypes="t_LanguageId t_LanguageIdNone"/>
  </xs:simpleType>
  <xs:simpleType name="t_LanguageId">
    <xs:restriction base="xs:language"/>
  </xs:simpleType>
  <xs:simpleType name="t_LanguageIdNone">
    <xs:restriction base="xs:token">
      <xs:enumeration value="none"/>
    </xs:restriction>
  </xs:simpleType>
  <!-- VCard -->
  <xs:simpleType name="t_VCard">
    <xs:restriction base="t_CharacterString"/>
  </xs:simpleType>
  <!-- MimeType -->
  <xs:simpleType name="t_MimeType">
    <xs:restriction base="t_CharacterString"/>
  </xs:simpleType>
  <!-- Size -->
  <xs:simpleType name="t_Size">
    <xs:restriction base="xs:nonNegativeInteger"/>
  </xs:simpleType>