- Go to https://www.wikidata.org/wiki/Q428581 (Possession book)
- at the bottom of Statements, click [add]
- choose publication date, enter 1990
- click [add reference]
Result: nothing happens (is it a bug that the UI doesn't show any error?). If you look in developer console, there's an error "Error: Required option not specified properly".
I found from ?debug=1 that the error is in jquery.wikibase.referenceview.js line 93 because this.options.statementGuid is null. It happens in Firefox and chromium.
Maybe I'm meant to save the statement first? But if I click Save, I get
TypeError: edittoolbar is undefined btnSave = edittoolbar.getButton( 'save' ), referenceview.js (line 73, col 5)
and again, no error shown to user.