**Steps to replicate the issue** (include links if applicable):
* Go edit some function like this one: https://wikifunctions.beta.wmflabs.org/w/index.php?title=Z10598&action=edit
* If there is not at least 2 arguments, add one, publish (save), and go back editing the function
* Remove the first input and publish the changes
**What happens?**:
The changes get rejected
**What should have happened instead?**:
The changes should be accepted
**Functional note**: if the second argument is removed instead of the first one, publishing the changes works
**Technical note**: seems like the instead of removing the first argument in the JSON submitted, the associated value is set to null:
```diff
11,36c11
< {
< "Z1K1": "Z17",
< "Z17K1": "Z6",
< "Z17K2": "Z10053K1",
< "Z17K3": {
< "Z1K1": "Z12",
< "Z12K1": [
< "Z11",
< {
< "Z1K1": "Z11",
< "Z11K1": "Z1002",
< "Z11K2": "foo"
< },
< {
< "Z1K1": "Z11",
< "Z11K1": "Z1004",
< "Z11K2": "foo"
< }
< ]
< }
< },
---
> null,
```