Front-end allows creating a trigger that closes problems by tag when there are no tags configured. This is most likely a mis-configuration.

A more nuanced case - all of the tags have fixed names (e.g. string literals or LLD macros). None of the macros match the macro configured for correlation. Should there be an error in this case? This could happen due to typo, for example.

If we fix this in front-end then we have to fix this in DB during upgrade as well. Probably no changes in server, but have to check.

(see also ZBXNEXT-3457)