Context menu item "Change Field for Items" does not work

I discovered there is a context menu item in Zotero 4.0.9 (Firefox plugin) called "Change Field for Items", which opens a dialog that supposedly lets you bulk update a specific field in multiple items. But even a trivial test does not work.
The dialog shows two text fields, "Field to change" and "Value", and a checkbox "Overwrite?". Usage seemed obvious, but when I put in "Date" and "2013" for one item that has no date yet, nothing happens and two lines are added to the error log.

There doesn't appear to be any documentation for this function - neither a forums search nor a Google search for 'zotero "change field for items"' returns anything with those exact terms.

I reported errors under reference 1563701754. That report includes more than just the lines produced by this function, which in themselves do not appear very descriptive.

I apologise if it turns out that this is a function introduced by Paper Machines and this is the wrong forum for questions about it. :)
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