Steps to replicate the issue (include links if applicable):
Go to the fallback editor for an existing function.
Add a couple of alias labels for the function name (in the labels box at the top).
Delete one of the alias labels (not the last).

What happens?:
The zObject viewer updates but stores a "null" value for the deleted label instead of just removing it.

"Z2K4": {
        "Z1K1": "Z32",
        "Z32K1": [
            "Z31",
            {
                "Z1K1": "Z31",
                "Z31K1": "Z1002",
                "Z31K2": [
                    "Z6",
                    "my night memories",
                    null,
                    "sleepy saver"
                ]
            }
        ]

What should have happened instead?:
The item is just removed from the list

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):