With Hibernate ORM 5.3, protect against NPE in WildFlyCustomRegionFactoryInitiator for non-container-managed JPA deployment

	  at org.jboss.as.jpa.hibernate5.service.WildFlyCustomRegionFactoryInitiator.resolveRegionFactory(WildFlyCustomRegionFactoryInitiator.java:44)
	  at org.hibernate.cache.internal.RegionFactoryInitiator.initiateService(RegionFactoryInitiator.java:47)
	  at org.hibernate.cache.internal.RegionFactoryInitiator.initiateService(RegionFactoryInitiator.java:32)
	  at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:94)
	  at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:263)
	  at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:237)
	  at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:214)
	  - locked <0x4fcc> (a org.hibernate.boot.registry.internal.StandardServiceRegistryImpl)
	  at org.hibernate.boot.internal.MetadataBuilderImpl$MetadataBuildingOptionsImpl.<init>(MetadataBuilderImpl.java:688)
	  at org.hibernate.boot.internal.MetadataBuilderImpl.<init>(MetadataBuilderImpl.java:123)
	  at org.hibernate.boot.MetadataSources.getMetadataBuilder(MetadataSources.java:136)
	  at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:213)
	  at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:169)
	  at org.hibernate.jpa.boot.spi.Bootstrap.getEntityManagerFactoryBuilder(Bootstrap.java:76)
	  at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilder(HibernatePersistenceProvider.java:179)
	  at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilderOrNull(HibernatePersistenceProvider.java:127)
	  at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilderOrNull(HibernatePersistenceProvider.java:69)
	  at org.hibernate.jpa.HibernatePersistenceProvider.generateSchema(HibernatePersistenceProvider.java:164)
	  at javax.persistence.Persistence.generateSchema(Persistence.java:114)