Song/Album submit not working

[Shiroizu]

https://vocadb.net/Song/Create

Artist search box is not functioning.

Error on web console:

Uncaught TypeError: t is null
value https://vocadb.net/bundles/vdb.js?id=dc4f84b0a86b6a2d5224:1
...
https://vocadb.net/bundles/shared/libs.js?id=db0c5e00d4c10a8d69c2:1

(Same error as with #1012)

[ycanardeau]

Caused by #1007. The tag parameter of the details_tag_contract function may be undefined, so we need to check if it is undefined first. As stated in #900, it's difficult to catch JavaScript errors in cshtml files at compile time.