In json, it is null. The value in the frame is blank.
This tutorial explains how to set localization: https://www.webdatarocks.com/doc/language-localization/. When setting the link to en.json, open this file, find “blankMember“: “(blank)“, and replace with the desired value.
Link to en.json: https://github.com/WebDataRocks/pivot-localizations/blob/master/en.json
Hope it helps.