patch 9.0.1934: :bwipe fails after switching window from aucmd_win.

Problem:  :bwipe fails after switching window from aucmd_win.
Solution: Decrement b_nwindows after switching back to aucmd_win.

closes: #13160

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/autocmd.c b/src/autocmd.c
index 63e5673..c09e12f 100644
--- a/src/autocmd.c
+++ b/src/autocmd.c
@@ -1635,7 +1635,6 @@
     {
 	win_T *awp = aucmd_win[aco->use_aucmd_win_idx].auc_win;
 
-	--curbuf->b_nwindows;
 	// Find "awp", it can't be closed, but it may be in another tab
 	// page. Do not trigger autocommands here.
 	block_autocmds();
@@ -1656,8 +1655,8 @@
 	    }
 	}
 win_found:
+	--curbuf->b_nwindows;
 #ifdef FEAT_JOB_CHANNEL
-	;
 	int save_stop_insert_mode = stop_insert_mode;
 	// May need to stop Insert mode if we were in a prompt buffer.
 	leaving_window(curwin);