bug#8911: bs-cycle-next deletes window in some cases.

[Stefan Monnier]

>> emacs -Q -l bs
>> C-h N
>> C-h C-c
>> M-: (set-window-dedicated-p (selected-window) t) <RET>
>> M-x bs-cycle-next <RET>
>> of splitting the window extremely unuseful and unhelpful.
> But that's the semantics of (set-window-dedicated-p (selected-window) t).

Sorry, you're right.  The right thing to do here is to signal an error,
not to split the window.


        Stefan