fixed npe in OneToManyRelationMetadataProcessor

When trying to use inheritance and one-to-many collections I keep getting null pointers.  This commit seems to do the trick.  Stack trace below: 

java.lang.NullPointerException
	at com.impetus.kundera.metadata.processor.relation.OneToManyRelationMetadataProcessor.addRelationIntoMetadata(OneToManyRelationMetadataProcessor.java:93)
	at com.impetus.kundera.metadata.processor.TableProcessor.addRelationIntoMetadata(TableProcessor.java:181)
	at com.impetus.kundera.metadata.processor.TableProcessor.populateMetadata(TableProcessor.java:147)
	at com.impetus.kundera.metadata.processor.TableProcessor.process(TableProcessor.java:87)
	at com.impetus.kundera.metadata.MetadataBuilder.buildEntityMetadata(MetadataBuilder.java:131)
	at com.impetus.kundera.configure.MetamodelConfiguration.scanClassAndPutMetadata(MetamodelConfiguration.java:391)
	at com.impetus.kundera.configure.MetamodelConfiguration.loadEntityMetadata(MetamodelConfiguration.java:230)
	at com.impetus.kundera.configure.MetamodelConfiguration.configure(MetamodelConfiguration.java:102)
	at com.impetus.kundera.configure.Configurator.configure(Configurator.java:65)
	at com.impetus.kundera.KunderaPersistence.initializeKundera(KunderaPersistence.java:109)
	at com.impetus.kundera.KunderaPersistence.createEntityManagerFactory(KunderaPersistence.java:81)
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)