Impala throws IllegalStateException when [SHUFFLE] inserting data into a partition while select subquery group by partition columns

[localhost:21000] > create table part_test (col int) partitioned by (p int);
Query: create table part_test (col int) partitioned by (p int)
Query submitted at: 2016-07-28 09:39:36 (Coordinator: http://0.0.0.0:25000)
Query progress can be monitored at: http://0.0.0.0:25000/query_plan?query_id=964bb7eaf152615f:bc435fa67a22929f

Fetched 0 row(s) in 0.40s
[localhost:21000] > create table test(col1 int, p int);
Query: create table test(col1 int, p int)
Query submitted at: 2016-07-28 09:39:44 (Coordinator: http://0.0.0.0:25000)
Query progress can be monitored at: http://0.0.0.0:25000/query_plan?query_id=b40048f323fd53f:d94599b286e4da9d

Fetched 0 row(s) in 0.11s
[localhost:21000] > insert overwrite table part_test partition (p=1) select max(col1) as col from test group by p;
Query: insert overwrite table part_test partition (p=1) select max(col1) as col from test group by p
Query submitted at: 2016-07-28 09:39:51 (Coordinator: http://0.0.0.0:25000)
Query progress can be monitored at: http://0.0.0.0:25000/query_plan?query_id=704225bd24a68554:bc7b1374380872a2
Inserted 0 row(s) in 5.36s
[localhost:21000] > insert overwrite table part_test partition (p=1) [SHUFFLE] select max(col1) from test group by p;
Query: insert overwrite table part_test partition (p=1) [SHUFFLE] select max(col1) from test group by p
Query submitted at: 2016-07-28 09:40:08 (Coordinator: http://0.0.0.0:25000)
ERROR: IllegalStateException: null

[localhost:21000] > explain insert overwrite table part_test partition (p=1) [SHUFFLE] select max(col1) from test group by p;                 
Query: explain insert overwrite table part_test partition (p=1) [SHUFFLE] select max(col1) from test group by p
Query submitted at: 2016-07-28 09:41:38 (Coordinator: http://0.0.0.0:25000)
ERROR: IllegalStateException: null