Can you have optional measurements with max_by()?

Can you do a max_by() and not throw an error if the column doesn't exist?

select customer, site, system, max(time),
	max_by("loads", time) as loads,
	max_by("weight", time) as lbs,
	max_by("turns", time) as turns
from "x"."x-test" 
where time > ago(12h)
 AND customer='TEST'
 AND site='TEST'
 AND system='TEST'
 AND measure_name = 'system-status'
GROUP BY customer, site, system

The probably really is that I want to return max_by("*", time) but that's not possible. The problem is that max_by() won't return null if the column doesn't exist; it will just throw an exception.

I am working off of this doc section 1 (last value queries) as my template. I can use the first example (WITH ... SELECT ...) but as the document points out this is more expensive. It'd be better to use max_by() but not have it flip out of 'weight' or 'turns' is not in that particular MULTI record.