Drill is not displaying the column when the json has a null value for the column and the file contains a single record

{
  "a" : null,
  "b" : 1
}

select * from `temp.json`;
+------------+
|     b      |
+------------+
| 1          |
+------------+

{
  "a" : null,
  "b" : 1
}
{
  "a" : 1,
  "b" : null
}

select * from `temp.json`;
+------------+------------+
|     b      |     a      |
+------------+------------+
| 1          | null       |
| null       | 1          |
+------------+------------+