Traceback when listing packages with empty fields

[citrus-it]

Traceback (most recent call last):
  File "/usr/bin/pkg", line 7797, in handle_errors
    __ret = func(*args, **kwargs)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/pkg", line 7782, in main_func
    return func(op=subcommand, api_inst=api_inst, pargs=pargs, **opts)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/pkg", line 849, in list_inventory
    fmt_str = calc_fmtstr(attrs, data)
              ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/pkg", line 648, in calc_fmtstr
    if len(entry.get(field)) > widths[i]:
       ^^^^^^^^^^^^^^^^^^^^^
TypeError: object of type 'NoneType' has no len()