Imported font family through the theme editor creates an entry in the Font Family drop -down fields. Once created, the new font family is available for use in the theme and style preset variables. In some instances, adding a new font in the theme editor causes it to crash with the error message:
TypeError: Cannot read properties of null (reading 'join')
An error while attempting to import a font to the theme editor may happen when using our native file uploading service, as well as other font hosting providers. The font import may fail due to missing information during the parsing process.
To fix this issue, remove the imported font that causes the theme editor to crash, and use fonts in the Google Fonts library, instead.