bug#50576: 28.0.50; display-buffer-in-previous-window no longer accepts window value for previous-window

[Adam Porter]

Hi Juri, et al,

It seems the patch in this message:

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=45688#116

which was installed causes the function
display-buffer-in-previous-window to fail when called with an alist
having the previous-window key set to a window value, because it calls
boundp on the value unconditionally rather than checking the type of
the value.