NPE when using avg on repeated property and one group does not contain any value

   public void testEmbeddedAvg() {
      QueryFactory qf = getQueryFactory();
      Query q = qf.from(getModelFactory().getUserImplClass())
            .select(Expression.property("surname"), Expression.avg("addresses.number"))
            .groupBy("surname")
            .orderBy("surname")
            .build();

      List<Object[]> list = q.list();
      assertEquals(3, list.size());
      assertEquals(2, list.get(0).length);
      assertEquals(2, list.get(1).length);
      assertEquals(2, list.get(2).length);
      assertEquals(156d, (Double) list.get(0)[1], 0.0001d);
      assertEquals(150d, (Double) list.get(1)[1], 0.0001d);
      assertEquals(null, list.get(2)[1]);
   }

java.lang.NullPointerException
	at org.infinispan.objectfilter.impl.aggregation.AvgAccumulator.merge(AvgAccumulator.java:39)
	at org.infinispan.objectfilter.impl.aggregation.FieldAccumulator.merge(FieldAccumulator.java:42)
	at org.infinispan.objectfilter.impl.aggregation.Grouper.addRow(Grouper.java:133)
	at org.infinispan.query.dsl.embedded.impl.AggregatingQuery.getBaseIterator(AggregatingQuery.java:52)
	at org.infinispan.query.dsl.embedded.impl.HybridQuery$1.<init>(HybridQuery.java:47)
	at org.infinispan.query.dsl.embedded.impl.HybridQuery.getIterator(HybridQuery.java:45)
	at org.infinispan.query.dsl.embedded.impl.BaseEmbeddedQuery.listInternal(BaseEmbeddedQuery.java:65)
	at org.infinispan.query.dsl.embedded.impl.BaseEmbeddedQuery.list(BaseEmbeddedQuery.java:57)
	at org.infinispan.query.dsl.embedded.impl.DelegatingQuery.list(DelegatingQuery.java:45)
	at org.infinispan.query.dsl.embedded.QueryDslConditionsTest.testEmbeddedAvg(QueryDslConditionsTest.java:2066)