Assert in a query with both avg aggregate and avg window aggregate functions

0: jdbc:drill:schema=dfs> select avg(a1), avg(a1) over () from t1 group by a1;
Error: SYSTEM ERROR: AssertionError: Internal error: invariant violated: conversion result not null
[Error Id: 2f850005-a7f6-4215-bbc1-90da57cbb71f on atsqa4-133.qa.lab:31010] (state=,code=0)

0: jdbc:drill:schema=dfs> select avg(a1), sum(a1) over () from t1 group by a1;
+---------+---------+
| EXPR$0  | EXPR$1  |
+---------+---------+
| 1.0     | 47      |
| 2.0     | 47      |
| 3.0     | 47      |
| 4.0     | 47      |
| 5.0     | 47      |
| 6.0     | 47      |
| 7.0     | 47      |
| 9.0     | 47      |
| 10.0    | 47      |
| null    | 47      |
+---------+---------+
10 rows selected (0.54 seconds)

0: jdbc:drill:schema=dfs> select avg(a1), count(a1) over () from t1 group by a1;
+---------+---------+
| EXPR$0  | EXPR$1  |
+---------+---------+
| 1.0     | 9       |
| 2.0     | 9       |
| 3.0     | 9       |
| 4.0     | 9       |
| 5.0     | 9       |
| 6.0     | 9       |
| 7.0     | 9       |
| 9.0     | 9       |
| 10.0    | 9       |
| null    | 9       |
+---------+---------+
10 rows selected (0.304 seconds)

0: jdbc:drill:schema=dfs> select avg(a1), count(a1) over (), sum(a1) over(partition by b1) from t1 group by a1, b1;
+---------+---------+---------+
| EXPR$0  | EXPR$1  | EXPR$2  |
+---------+---------+---------+
| 1.0     | 9       | 1       |
| 2.0     | 9       | 2       |
| 3.0     | 9       | 3       |
| 5.0     | 9       | 5       |
| 6.0     | 9       | 6       |
| 7.0     | 9       | 7       |
| null    | 9       | null    |
| 9.0     | 9       | 9       |
| 10.0    | 9       | 10      |
| 4.0     | 9       | 4       |
+---------+---------+---------+
10 rows selected (0.788 seconds)

2015-08-15 00:06:20,260 [2a317d83-5099-1d1f-ba86-33173f88b00c:foreman] INFO  o.a.drill.exec.work.foreman.Foreman - State change requested.  PENDING --> FAILED
org.apache.drill.exec.work.foreman.ForemanException: Unexpected exception during fragment initialization: Internal error: while converting `CastHigh`(SUM(`t1`.`a1`)) / COUNT(`t1`.`a1`)
        at org.apache.drill.exec.work.foreman.Foreman.run(Foreman.java:253) [drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_71]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_71]
        at java.lang.Thread.run(Thread.java:745) [na:1.7.0_71]
Caused by: java.lang.AssertionError: Internal error: while converting `CastHigh`(SUM(`t1`.`a1`)) / COUNT(`t1`.`a1`)
        at org.apache.calcite.util.Util.newInternal(Util.java:790) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.ReflectiveConvertletTable$1.convertCall(ReflectiveConvertletTable.java:96) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlNodeToRexConverterImpl.convertCall(SqlNodeToRexConverterImpl.java:60) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter$Blackboard.visit(SqlToRelConverter.java:4070) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter$Blackboard.visit(SqlToRelConverter.java:3508) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:130) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter$Blackboard.convertExpression(SqlToRelConverter.java:3963) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.drill.exec.planner.sql.DrillAvgVarianceConvertlet.convertCall(DrillAvgVarianceConvertlet.java:72) ~[drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.calcite.sql2rel.SqlNodeToRexConverterImpl.convertCall(SqlNodeToRexConverterImpl.java:60) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertOver(SqlToRelConverter.java:1762) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.access$1000(SqlToRelConverter.java:180) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter$Blackboard.convertExpression(SqlToRelConverter.java:3956) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.createAggImpl(SqlToRelConverter.java:2539) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertAgg(SqlToRelConverter.java:2360) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertSelectImpl(SqlToRelConverter.java:604) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertSelect(SqlToRelConverter.java:564) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertQueryRecursive(SqlToRelConverter.java:2759) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.sql2rel.SqlToRelConverter.convertQuery(SqlToRelConverter.java:522) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.calcite.prepare.PlannerImpl.convert(PlannerImpl.java:198) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        at org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.convertToRel(DefaultSqlHandler.java:450) ~[drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.validateAndConvert(DefaultSqlHandler.java:193) ~[drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.getPlan(DefaultSqlHandler.java:159) ~[drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.drill.exec.planner.sql.DrillSqlWorker.getPlan(DrillSqlWorker.java:178) ~[drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.drill.exec.work.foreman.Foreman.runSQL(Foreman.java:903) [drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        at org.apache.drill.exec.work.foreman.Foreman.run(Foreman.java:242) [drill-java-exec-1.2.0-SNAPSHOT.jar:1.2.0-SNAPSHOT]
        ... 3 common frames omitted
Caused by: java.lang.reflect.InvocationTargetException: null
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_71]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_71]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_71]
        at java.lang.reflect.Method.invoke(Method.java:606) ~[na:1.7.0_71]
        at org.apache.calcite.sql2rel.ReflectiveConvertletTable$1.convertCall(ReflectiveConvertletTable.java:87) ~[calcite-core-1.1.0-drill-r16.jar:1.1.0-drill-r16]
        ... 26 common frames omitted