PDFBOX-1642: NPE onClosed Choice
* Fixed NPE, "closed Choice of Text" was not a known type
* Trim namespaces parameter in schema definition (see line 17 of attached xmp)

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1546743 13f79535-47bb-0310-9956-ffa450edef68