When using a <join> with <subselect> in hbm configuration, a NullPointerException is thrown due to an empty table name:

Caused by: java.lang.NullPointerException
at org.hibernate.sql.Alias.toAliasString(Alias.java:38)
at org.hibernate.mapping.Join.createPrimaryKey(Join.java:95)
at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindSecondaryTable(ModelBinder.java:1819)
at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindAllEntityAttributes(ModelBinder.java:1114)
at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindRootEntity(ModelBinder.java:265)
at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindEntityHierarchy(ModelBinder.java:185)
at org.hibernate.boot.model.source.internal.hbm.HbmMetadataSourceProcessorImpl.processEntityHierarchies(HbmMetadataSourceProcessorImpl.java:144)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:218)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:265)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83)