fix: error 400 for posting a publication with an empty json

https://issues.unige.ch/browse/AOU-311

AoU-ResourceServerCommon/src/main/java/ch/unige/aou/service/metadata/MetadataExtractorV1.java

@@ -30,7 +30,9 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 
 import ch.unige.solidify.exception.SolidifyResourceNotFoundException;
 import ch.unige.solidify.exception.SolidifyRuntimeException;
+import ch.unige.solidify.exception.SolidifyValidationException;
 import ch.unige.solidify.util.StringTool;
+import ch.unige.solidify.validation.ValidationError;
 
 import ch.unige.aou.business.ContributorService;
 import ch.unige.aou.business.LanguageService;
@@ -135,7 +137,6 @@ import ch.unige.aou.model.xml.deposit.v1.serializer.TextSerializer;
 
 @Service
 public class MetadataExtractorV1 extends MetadataExtractor {
-
   public MetadataExtractorV1(PublicationTypeService publicationTypeService, PublicationSubtypeService publicationSubtypeService,
           PublicationSubSubtypeService publicationSubSubtypeService, StructureService structureService,
           ResearchGroupService researchGroupService, ContributorService contributorService, LanguageService languageService) {
@@ -435,6 +436,9 @@ public class MetadataExtractorV1 extends MetadataExtractor {
   }
 
   private DepositDoc createDepositDocFromXml(String xmlData) {
+    if (xmlData == null) {
+      throw new SolidifyValidationException(new ValidationError("XmlData is null. Unable to deserialize XML to DepositDoc."));
+    }
     return JAXB.unmarshal(new StringReader(xmlData), DepositDoc.class);
   }