patch 8.2.0371: crash with combination of terminal popup and autocmd

Problem:    Crash with combination of terminal popup and autocmd.
Solution:   Disallow closing a popup that is the current window.  Add a check
            that the current buffer is valid. (closes #5754)

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    371,
 /**/
     370,
 /**/