Aperture photometry: if delete all subsets, no more access to table in the GUI

[Jdaviz-Triage-Bot]

Reporter: Camilla Pacifici

Create a subset, use simple aperture photometry on subset, entry is in table.
Delete subset, table disappears.
Create a new subset, table is back with all appropriate rows.

It would be useful to be able to see the table in GUI even when all subsets have been deleted.

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DISCLAIMER: This issue was autocreated by the Jdaviz Issue Creation Bot on behalf of the reporter. If any information is incorrect, please contact Duy Nguyen