vim-patch:8.2.4609: :unhide does not check for failing to close a window (#25317)

Problem:    :unhide does not check for failing to close a window.
Solution:   When closing a window fails continue with the next one.  Do not
            try closing the autocmd window. (closes vim/vim#9984)

6f2465d336

Co-authored-by: Bram Moolenaar <Bram@vim.org>

test/old/testdir/test_autocmd.vim

@@ -4,6 +4,7 @@ source shared.vim
 source check.vim
 source term_util.vim
 source screendump.vim
+source vim9.vim
 source load.vim
 
 func s:cleanup_buffers() abort
@@ -3432,6 +3433,20 @@ func Test_autocmd_vimgrep()
   augroup END
 endfunc
 
+func Test_closing_autocmd_window()
+  let lines =<< trim END
+      edit Xa.txt
+      tabnew Xb.txt
+      autocmd BufEnter Xa.txt unhide 1
+      doautoall BufEnter
+  END
+  call CheckScriptFailure(lines, 'E814:')
+  au! BufEnter
+  only!
+  bwipe Xa.txt
+  bwipe Xb.txt
+endfunc
+
 func Test_bufwipeout_changes_window()
   " This should not crash, but we don't have any expectations about what
   " happens, changing window in BufWipeout has unpredictable results.