Presence of an empty aggregation should not lead to Exceptions

  @Test public void testEmptyAggregateNotCausesException() throws Exception {
    final FrameworkConfig config = RelBuilderTest.config().build();
    final RelBuilder builder = RelBuilder.create(config);

    RelMetadataQuery mq = RelMetadataQuery.instance();
    RelNode agg = builder
        .scan("EMP")
        .aggregate(builder.groupKey(), Collections.<AggCall> emptyList()).build();
    mq.getTableOrigin(agg);
  }

java.lang.IndexOutOfBoundsException: index (0) must be less than size (0)
	at com.google.common.base.Preconditions.checkElementIndex(Preconditions.java:310)
	at com.google.common.base.Preconditions.checkElementIndex(Preconditions.java:293)
	at com.google.common.collect.RegularImmutableList.get(RegularImmutableList.java:67)
	at org.apache.calcite.rel.metadata.RelMdColumnOrigins.getColumnOrigins(RelMdColumnOrigins.java:77)
	at GeneratedMetadataHandler_ColumnOrigin.getColumnOrigins_$(Unknown Source)
	at GeneratedMetadataHandler_ColumnOrigin.getColumnOrigins(Unknown Source)
	at org.apache.calcite.rel.metadata.RelMetadataQuery.getColumnOrigins(RelMetadataQuery.java:345)
	at org.apache.calcite.rel.metadata.RelMetadataQuery.getTableOrigin(RelMetadataQuery.java:418)
	at org.apache.calcite.test.RelMetadataTest.testEmptyAggregateNotCausesException(RelMetadataTest.java:2396)