Median treats nulls as zero

[bijington]

Describe the bug
When performing a Median function nulls are treated as zeros and can skew results. Propose that nulls should simply be ignored.

To Reproduce
Median(10, 20, null)

Expected behavior
The above function should yield 15.

Platform (please complete the following information):

• Environment: https://bijington.github.io/expressive-playground/
• Version 2.4.0

Additional context
Add any other context about the problem here.