This should be a namespace, not an attribute "namespace"

Change-Id: I159db32662679a3194edf942fa6672370e2b8587
Reviewed-on: https://gerrit.libreoffice.org/40072Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>

xmlsecurity/source/helper/xsecctl.cxx

@@ -749,13 +749,11 @@ void XSecController::exportSignature(
                     }
 
                     /* Write PGPOwner element */
-                    pAttributeList = new SvXMLAttributeList();
-                    pAttributeList->AddAttribute("namespace", "loext");
                     xDocumentHandler->startElement(
-                        "PGPOwner",
-                        cssu::Reference< cssxs::XAttributeList >(pAttributeList));
+                        "loext:PGPOwner",
+                        cssu::Reference< cssxs::XAttributeList >(new SvXMLAttributeList()));
                     xDocumentHandler->characters( signatureInfo.ouGpgOwner );
-                    xDocumentHandler->endElement( "PGPOwner" );
+                    xDocumentHandler->endElement( "loext:PGPOwner" );
                 }
                 xDocumentHandler->endElement( "PGPData" );
             }