The NeatlineMaps plugin is severely broken and destroys your instance of Omeka. Please remove this from the plugins page. I’m baffled why it’s there when this is the result.
On a related note, since I had to erase the plugin directory to fix Omeka, how can I uninstall a broken and deleted plugin? The UI lists the plugin as not valid, I’d like to clear that out.
NeatlineTime is also defective and should be removed as it apparently has never worked. I don’t know how these get published on the site, but clearly they need better vetting.
Third party plugins like Neatline are always welcome, with the hope that maintainers will address bugs reported. Bugs with it should be reported on their GitHub issues page. Any number of plugins (including our own) have had unexpected issues on different systems and setups, so filing a report improves the plugin for everyone (though I understand that open source software can be subject to the availability of developer time).
Any plugin that doesn’t work on one system might work fine on another, so we don’t remove a plugin based on bug being discovered. Neatline plugins have had a pretty good track record.
To uninstall a plugin, the plugin generally has to be available on the file system. The only other option is to directly change the database. So, the best thing to try first is to replace the plugin and see if it is possible to uninstall it from the plugins list.
We’ve removed NeatlineMaps from the directory at the developer’s request; it was only ever intended for much older versions of Omeka.
If you’ve installed it and it’s causing problems, simply deleting the plugin’s folder should get you back up and running.