PR #7231 updated visualization validation to take place in the exploreReducer.js SET_FIELD_VALUE action. This validation does not take into account any controlOverrides on the visualization.
Specifically, the Table viz removes any validatation from the metrics row control. This means attempting to create a Table with only "Not Grouped By" columns fails.
Be able to create a Table visualization with only "Not Grouped By" columns
Creating any Table without a "Metrics" results in an error

Master branch as of April 22 (commit: 845218dd88ad2fe1284dcb7427c5bff20749dc74)
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I think we should reopen this issue and it's important to fix.
+1 on this. I am able to skirt around the issue by first defining "Not Grouped By" columns, and then clearing the 'Metrics' field.
The other way to workaround is to change Vis Type to something else and change is back to Table. Or just select Table explicitly (even if it is already selected) after Explore page loaded before changing any settings.
I could not reproduce on master. Loaded up a table chart and cleared Metrics field.

@mistercrunch I also tested on master and it doesn't reproduce for me either when loading from a chart. But on the other hand when going through Sources -> Tables, choosing birth_names, for example, and clearing COUNT metric, it does appear for me (tested on Chrome, Opera).
This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. For admin, please label this issue .pinned to prevent stale bot from closing the issue.
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I think we should reopen this issue and it's important to fix.