Do not write an empty <ModificationsList> element when there are no m…

…odifications with Unimod Ids. Instead write:

<cvParam cvRef="MS" accession="MS:1002864" name="No PTMs are included in the dataset"/> so that we do not get XML validations errors from ProteomeXchange.
Modifications without Unimod Ids are not supported by ProteomeXchange so we skip writing them to the XML file that is submitted to ProteomeXchange.

panoramapublic/src/org/labkey/panoramapublic/proteomexchange/PxXmlWriter.java

@@ -391,7 +391,7 @@ void writeModificationList(Status validationStatus) throws PxException
          */
         Element mod_list = new Element("ModificationList");
         var mods = validationStatus.getModifications();
-        if(mods.size() == 0)
+        if(mods.size() == 0 || mods.stream().noneMatch(Modification::isValid))
         {
             mod_list.addChild(new CvParamElement("MS", "MS:1002864", "No PTMs are included in the dataset"));
         }