Describe the bug
It is very easy to have an empty Paragraph block end up in an otherwise empty widget area.

To reproduce
Steps to reproduce the behavior:

1. Go to widgets screen
2. Remove all widgets
3. Click into empty widget area
4. Save settings

Expected behavior
It should be less easy to have an empty block in a widget area. Some themes will check for contents in a widget area as a mechanism to determine whether or not to output the wrapper HTML. Others will have styling that will create a visibly empty container.

Editor version (please complete the following information):

• WordPress version: 5.5.1
• If the Gutenberg plugin is installed, which version is it? 9.1.1

Additional context
Also worth noting that I've seen cases where adding an empty widget as a workaround to avoid default widget content without displaying any actual content. Having an empty column in a multi-column footer, for example. Not really a good practice but it does happen.