Do Not Import Empty Custom Fields from Buttercup CSV

[tnewman]

I recently imported my passwords to Buttercup using a CSV file, and it imported every blank custom field into the password manager.

For example, one of my entries had a custom field called "Account Number", and every entry now has a blank field called "Account Number".

Upon import, Buttercup should ignore blank custom fields.

I am willing to take on this development effort if this is functionality that the core team supports.

https://github.com/buttercup/buttercup-importer/blob/master/source/importers/ButtercupCSVImporter.js