`BaseWindow.to_tables` adding phantom tables?

[fjaviersanchez]

I have a sacc object with 27 bandpower windows, and when I try to write it and/or read it from firecrown it generates a couple of "phantom" tables that break a lot of things downstream. Here's a simplified example with S a sacc.Sacc object:

>>> from sacc.utils import unique_list
>>> import sacc.windows
>>> win_here = unique_list(d.get_tag('window') for d in S.data)
>>> len(win_here)
27
>>> tables_here = sacc.windows.BandpowerWindow.to_tables(win_here)
>>> len(tables_here)
27
>>> tables_here = sacc.windows.BaseWindow.to_tables(win_here)
>>> len(tables_here)
29