Replacing empty string column with null in Kusto - azure-data-explorer

Question

How do I replace empty (non null) column of string datatype with null value?
So say the following query returns non zero recordset:-
mytable | where mycol == ""
Now these are the rows with mycol containing empty strings. I want to replace these with nulls. Now, from what I have read in the kusto documentation we have datatype specific null literals such as int(null),datetime(null),guid(null) etc. But there is no string(null). The closest to string is guid, but when I use it in the following manner, I get an error:-
mytable | where mycol == "" | extend test = translate(mycol,guid(null))
The error:-
translate(): argument #0 must be string literal
So what is the way out then?
Update:-
datatable(n:int,s:string)
[
10,"hello",
10,"",
11,"world",
11,"",
12,""
]
| summarize myset=make_set(s) by n
If you execute this, you can see that empty strings are being considered as part of sets. I don't want this, no such empty strings should be part of my array. But at the same time I don't want to lose value of n, and this is exactly what will happen if I if I use isnotempty function. So in the following example, you can see that the row where n=12 is not returned, there is no need to skip n=12, one could always get an empty array:-
datatable(n:int,s:string)
[
10,"hello",
10,"",
11,"world",
11,"",
12,""
]
| where isnotempty(s)
| summarize myset=make_set(s) by n

Answer 1

There's currently no support for null values for the string datatype: https://learn.microsoft.com/en-us/azure/kusto/query/scalar-data-types/null-values
I'm pretty certain that in itself, that shouldn't block you from reaching your end goal, but that goal isn't currently clear.
[update based on your update:]
datatable(n:int,s:string)
[
10,"hello",
10,"",
11,"world",
11,"",
12,""
]
| summarize make_set(todynamic(s)) by n