Blank email address should not overwrite other blank email addresses

[efc]

A blank email address should not overwrite another blank email address when importing a CSV. Otherwise it is impossible to import more than one user in a single file without email addresses (which is actually allowed by the WordPress API).

The fix is pretty simple, replace this line...

if ( ! $user && isset( $userdata['user_email'] ) )

with this...

if ( ! $user && isset( $userdata['user_email'] ) && $userdata['user_email'] )

I hope this can be fixed in a future version. Thanks!