Fix misleading error with empty table list

[greenape]

Closes #436

I have:

• [x] Formatted any Python files with black
• [ ] Brought the branch up to date with master
• [x] Added any relevant Github labels
• [x] Added tests for any new additions
• [ ] Added or updated any relevant documentation
• [ ] Added an Architectural Decision Record (ADR), if appropriate
• [ ] Added an MPLv2 License Header if appropriate
• [x] Updated the Changelog

Description

Fixes the misleading missing dates error raised when passing an empty list of tables to EventsTablesUnion. Instead it will now raise a ValueError stating that the list must have table names in it, also raises sensible errors for empty strings, and things which are not strings.

[cypress[bot]]

---

Test summary

43 • 0 • 0 • 0 • 1

---

Run details

Project	FlowAuth
Status	Passed
Commit	af3e89ce56
Started	Nov 11, 2022 2:36 PM
Ended	Nov 11, 2022 2:59 PM
Duration	23:08 💡
OS	Linux Debian -
Browser	Electron 106

View run in Cypress Dashboard ➡️

---

Flakiness

	cypress/e2e/add_new_server.js		1
1	Server management > Add server

---

This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard