java.lang.NullPointerException
	at org.hibernate.mapping.Constraint$ColumnComparator.compare(Constraint.java:134)
	at org.hibernate.mapping.Constraint$ColumnComparator.compare(Constraint.java:130)
	at java.util.TimSort.countRunAndMakeAscending(TimSort.java:324)
	at java.util.TimSort.sort(TimSort.java:189)
	at java.util.TimSort.sort(TimSort.java:173)
	at java.util.Arrays.sort(Arrays.java:659)
	at org.hibernate.mapping.Constraint.generateName(Constraint.java:82)
	at org.hibernate.cfg.Configuration.buildUniqueKeyFromColumnNames(Configuration.java:1620)
	at org.hibernate.cfg.Configuration.buildUniqueKeyFromColumnNames(Configuration.java:1598)
	at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1434)