patch 8.2.2464: using freed memory if window closed in autocommand

Problem:    Using freed memory if window closed in autocommand. (houyunsong)
Solution:   Check the window still exists.

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2464,
 /**/
     2463,
 /**/