CSIP83 fails for additional structMaps without ID

[prettybits]

When a METS document has additional structMaps (as allowed by CSIP80) that don't have an @ID attribute validation fails for CSIP83 even though that is only specified for mets/structMap[@LABEL="CSIP"]/@ID, meaning any other map should be allowed to not have an ID.

Example snippet:

<mets:structMap TYPE="PHYSICAL" LABEL="CSIP" ID="uuid-68947745-f4f2-424a-a974-0214a5b114f9">
    <mets:div ID="PHYS_0000">
      <mets:div LABEL="Metadata" ID="uuid-ee40af18-9622-44ff-b9af-9bf7123d09d8" DMDID="MODS" />
      <mets:div ID="uuid-7f6a3a22-71ec-4f68-93a6-fe07d5e42831" LABEL="Representations/master">
        <mets:mptr xlink:type="simple" xlink:href="representations/master/METS.xml" xlink:title="uuid-1c12046f-88ed-45d8-99af-de5a24d49355" LOCTYPE="URL" />
      </mets:div>
      <mets:div ID="uuid-2cd4ff49-76eb-4529-8ced-5eb88e804767" LABEL="Representations/ocr-txt">
        <mets:mptr xlink:type="simple" xlink:href="representations/ocr-txt/METS.xml" xlink:title="uuid-44048f07-7883-424f-8bee-3c55bf055de4" LOCTYPE="URL" />
      </mets:div>
    </mets:div>
  </mets:structMap>
  <mets:structMap TYPE="LOGICAL">
    <mets:div DMDID="MODS" ID="LOG_0000" LABEL="Letter">
    </mets:div>
  </mets:structMap>

fails with

{
    "specification" : "CSIP-2.0.4",
    "id" : "CSIP83",
    "name" : "mets/structMap[@LABEL=’CSIP’]/@ID",
    "location" : "mets/structMap[@LABEL=’CSIP’]/@ID",
    "description" : "An xml:id identifier for the structural description (structMap) used for internal package references. It must be unique within the package.",
    "cardinality" : "1..1",
    "level" : "MUST",
    "testing" : {
      "outcome" : "FAILED",
      "issues" : [ "mets/structMap[@LABEL='CSIP']/@ID in Root METS.xml can't be null" ],
      "warnings" : [ ],
      "notes" : [ ]
    }
}