[UWS] Fix missing double quotes in the XML serialization of job parameters

passed by reference.

src/uws/job/serializer/XMLSerializer.java

@@ -41,7 +41,7 @@ import uws.service.request.UploadFile;
  * Lets serializing any UWS resource in XML.
  *
  * @author Grégory Mantelet (CDS;ARI)
- * @version 4.3 (03/2018)
+ * @version 4.3 (04/2018)
  */
 public class XMLSerializer extends UWSSerializer {
 	private static final long serialVersionUID = 1L;
@@ -433,7 +433,7 @@ public class XMLSerializer extends UWSSerializer {
 
 					// set if it is an uploaded file:
 					if (paramValue instanceof UploadFile)
-						buf.append(" byReference=\"true");
+						buf.append(" byReference=\"true\"");
 
 					/*
 					 * Note: