Reduce empty address lines in "details" output

[sciurius]

When formatting the postal address, empty fields cause empty lines and sometimes weird appearance. For example:

Address
    HOME: 
        Main street 20

        1234 AB Blaricum
        , Netherlands

This PR removes empty fields from the address structure so they do not cause misbehaviour.

After the patch:

Address
    HOME: 
        Main street 20
        1234 AB Blaricum
        Netherlands

[scheibler]

Thank you