vim-patch:8.2.2473: crash when leaving command line window triggers autocommand

Problem:    Crash when leaving command line window triggers autocommand.
            (houyunsong)
Solution:   Make sure not to close the current window or buffer.
8c6951fa28

N/A patches for version.c:

vim-patch:8.2.2414: using freed memory when closing the cmdline window

Problem:    Using freed memory when closing the cmdline window.
Solution:   Check the window is still valid.
b7e2670b6a

src/nvim/ex_getln.c

@@ -6635,11 +6635,13 @@ static int open_cmdwin(void)
     wp = curwin;
     set_bufref(&bufref, curbuf);
     win_goto(old_curwin);
-    win_close(wp, true);
+    if (win_valid(wp) && wp != curwin) {
+      win_close(wp, true);
+    }
 
     // win_close() may have already wiped the buffer when 'bh' is
-    // set to 'wipe'.
-    if (bufref_valid(&bufref)) {
+    // set to 'wipe', autocommands may have closed other windows
+    if (bufref_valid(&bufref) && bufref.br_buf != curbuf) {
       close_buffer(NULL, bufref.br_buf, DOBUF_WIPE, false);
     }
 

src/nvim/testdir/test_autocmd.vim

@@ -2000,4 +2000,13 @@ func Test_autocmd_closes_window()
   au! BufWinLeave
 endfunc
 
+func Test_autocmd_closing_cmdwin()
+  au BufWinLeave * nested q
+  call assert_fails("norm 7q?\n", 'E855:')
+
+  au! BufWinLeave
+  new
+  only
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab