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

SVN: 19950

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

@@ -150,12 +150,7 @@ abstract class AbstractTransactionState<T extends DataSetInformation>
                     new SampleIdentifierFactory(sampleIdentifierString).createIdentifier();
             ch.systemsx.cisd.openbis.generic.shared.basic.dto.Sample sample =
                     openBisService.tryGetSampleWithExperiment(sampleIdentifier);
-            // TODO KE: Ask Sekhar if we should throw an exception or simply return NULL
-            if (sample == null)
-            {
-                throw new IllegalArgumentException("Could not find sample with identifier"
-                        + sampleIdentifierString);
-            }
+
             Sample result = new Sample(sample);
             samplesToBeUpdated.add(result);
             return result;