Bug description

Description

The "schema" field is not required :

with version 4 value 'public' was set by default but with V5.0.0, the default value is not set

The error message should precise

The import is OK if user set a schema but 2 datasets are existing for 1 table

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

3.9

Node version

16

Browser

Chrome

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.