Default window parameter not used in lalpulsar_MakeSFTs

The default window parameter does not seem to be used when running lalpulsar_MakeSFTs when not passing this option. The default value is 0.001 for use with the default tukey window, but if the user does not pass the window parameter, L401 sets the window parameter to zero. This essentially forces the user to specify the window parameter instead of using defaults. It's not necessarily broken but the program doesn't work as expected and the output (consistent with tukey window + window parameter = 0) is confusing to the user.