patch 9.2.0252: Crash when ending Visual mode after curbuf was unloaded

patch 9.2.0252: Crash when ending Visual mode after curbuf was unloaded

Problem:  if close_buffer() in set_curbuf() unloads curbuf, NULL pointer
          accesses may occur from enter_buffer() calling
          end_visual_mode(), as curbuf is already abandoned and possibly
          unloaded.  Also, selection registers may not contain the
          selection with clipboard+=autoselect(plus).
Solution: Move close_buffer()'s end_visual_mode() call to buf_freeall(), after
          any autocmds that may restart it, but just before freeing anything
          (Sean Dewar)

related: #19728

Signed-off-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>