split-window-right doesn't work with wide margins

[Joost Kremers]

Hi all,

a recent change on emacs-25 seems to cause problems for
split-window-right when a window has wide margins. To reproduce, simply
create a wide frame with one window, create a wide right margin with
`M-: (set-window-margins nil nil 130)` and then `C-x 3`. This will
produce the following error

split-window: Window #<window 3 on *scratch*> too small for splitting (2)

Does anyone know what change may have caused this? And is it intentional
behaviour or should this be considered a bug?

TIA

Joost



-- 
Joost Kremers
Life has its moments