`MEDIAN` aggregation causes subsequent columns to return empty cells

[Schaechtle]

Examples of MEDIAN aggregation causing subsequent columns to return empty cells

iql> SELECT MEDIAN(Perigee_km), AVG(Perigee_km) FROM d

| MEDIAN(Perigee_km) | AVG(Perigee_km) |
|--------------------+-----------------|
|               1413 |                 |


iql> SELECT MEDIAN(Perigee_km), Perigee_km FROM d
| MEDIAN(Perigee_km) | Perigee_km |
|--------------------+------------|
|               1413 |            |

The following runs fine

iql> SELECT MEDIAN(Perigee_km) FROM d

| MEDIAN(Perigee_km) |
|--------------------|
|               1413 |


iql> SELECT AVG(Perigee_km), MEDIAN(Perigee_km) FROM d

|    AVG(Perigee_km) | MEDIAN(Perigee_km) |
|--------------------+--------------------|
| 15507.611492281303 |               1413 |

This was tested with the satellites data and with iql-strict.