/series/import/request/{id}(seller.url): trim empty value to null

[0pdd]

The puzzle 695-d7a72e2c from #695 has to be resolved:

mystamps/src/main/java/ru/mystamps/web/controller/dto/ImportSellerForm.java

Line 34 in 0acabfc

// @todo #695 /series/import/request/{id}(seller.url): trim empty values to null

The puzzle was created by Slava Semushin on 08-Feb-18.