Error: "Allowed File extensions have not been specified."

Hi.

In version 3.53, when editing an existing WYSIWYG field, if "Allow Uploads" is not checked and there are no "File extensions allowed" entered, clicking 'Save' causes a modal popup "Allowed File extensions have not been specified" and it's not possible to save the record (see screenshot).

Checking an older version (3.15), this did not happen, nor do remember it ever happening.

I can successfully save if I enter a blank space or fictitious file type, such as 'zzz', so nothing major - just thought I'd ask. I don't know if this is a new intended behavior or something for the next version fix list.

Thanks.
Deborah