• [ x] I've read the Troubleshooting First Steps
• [ x] This request isn't a duplicate of an existing issue, opened or closed
• [ x] I've read the docs and followed them (if applicable)
• [ x] This is not a personal support request that should be posted on the YOURLS Discourse community

Describe the bug
When is try to upgrade my Installation from 1.7.6 to 1.7.9 is get the following message after is need to click for an Database Upgrade:

Upgrade YOURLS

Updating DB. Please wait...

Unable to update the DB.

You will have to manually fix things, sorry for the inconvenience :(

The errors were:

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'A' for key 'PRIMARY'

To Reproduce
Steps to reproduce the behavior. This is mandatory if you expect someone to fix the problem. Example:

1. made via CLI git pull
2. Reload yourls
3. Get Message that DB-Update is need
4. See error

Expected behavior
Normally the Update show work

Actual behavior
nothing happens.. yourls does not work anymore

Screenshots
If applicable, add screenshots to help explain your problem.