[RP] BUG - 'defborder' with no argument

[Doug Kearns]

Problem: When no argument is given to defborder it is reset to a 'lucky
         lottery' number.

Fix: trivial - in cmd_defborder() return NULL at line 1854

On a similar note, I think that the bar_window, help_window and friends
should either respect the defborder setting or have another way to
specify it - defbarborder perhaps.

Regards,
Doug