minor: [LMS-2033] getSampleForUpdate() now returns NULL instead of throwing a runtime exception.

SVN: 19951

datastore_server/source/java/ch/systemsx/cisd/etlserver/registrator/api/v1/impl/AbstractTransactionState.java

@@ -151,8 +151,13 @@ abstract class AbstractTransactionState<T extends DataSetInformation>
             ch.systemsx.cisd.openbis.generic.shared.basic.dto.Sample sample =
                     openBisService.tryGetSampleWithExperiment(sampleIdentifier);
 
-            Sample result = new Sample(sample);
-            samplesToBeUpdated.add(result);
+            Sample result = null;
+            if (sample != null)
+            {
+                result = new Sample(sample);
+                samplesToBeUpdated.add(result);
+            }
+
             return result;
         }