Fix audit middle-entity table generation to add additional columns co…

…rrectly.

hibernate-core/src/main/java/org/hibernate/envers/configuration/internal/metadata/CollectionMetadataGenerator.java

@@ -851,7 +851,7 @@ private Element createMiddleEntityXml(String auditMiddleTableName, String auditM
 				isEmbeddableElementType()
 		);
 
-		mainGenerator.addAdditionalColumns( middleEntityXmlId );
+		mainGenerator.addAdditionalColumns( middleEntityXml );
 
 		// All other properties should also be part of the primary key of the middle entity.
 		return middleEntityXmlId;