Fix the flag of the Empire of Vietnam (section) [Risolto]

The Empire of Vietnam (section) issuer doesn't have its own flag so it just inherits the modern flag of Vietnam as that's the parent issuer. This is anachronistic as now a bunch of medieval to 19th century coins have the modern, communist Vietnamese flag on them.

Please change the flag of the Empire of Vietnam (section) issuer to use the flag of the Empire of Vietnam as well:

So a bunch of sub-issuers (various dynastic rebels) will inherit that.

This is pretty much the same situation than with the Empire of China and the Chinese provinces, on both of them I've recent topics. 

Fixed, thanks. 

PS: It might take some time to correctly appear.

Thank you!

Just a small update. The new flag does propagate to the coins properly, but the flag in the dropdown menu of the issuers is just an empty placeholder.