Bug: Series isn't being caught by duplication check

Description of your request or bug report: For some reason, the book importer looks like it’ll let me add ワンパンマン to Natively even though the series already exists here:

Also, oddly, there’s no sync series button on the LN ワンパンマン series page.

Trello link: (leave in blank)

Seems like now the system has the sync button and it’s finding the duplicate for both the digital and paper versions, so going ahead and marking this as fixed at some point.