PDFBOX-6203: reset reused object keys to avoid gaps in the xref table of the splitted document

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1934197 13f79535-47bb-0310-9956-ffa450edef68

Author: lehmi

pdfbox/src/main/java/org/apache/pdfbox/multipdf/Splitter.java

@@ -784,6 +784,8 @@ protected PDDocument createNewDocument() throws IOException
         destCatalog.setLanguage(sourceCatalog.getLanguage());
         destCatalog.setMarkInfo(sourceCatalog.getMarkInfo());
         destCatalog.setMetadata(sourceCatalog.getMetadata());
+        // reset reused object keys to avoid gaps in the xref table
+        destCatalog.getCOSObject().resetImportedObjectKeys();
         return document;
     }