patch 9.1.0471: Crash when using autocmd_get() after removing event inside autocmd

Problem:  Crash when using autocmd_get() after removing event inside
          autocmd (Sergey Vlasov)
Solution: Check that the pattern is NULL (zeertzjq).

fixes: #14937
closes: #14939

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 50a34c8..40186dd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    471,
+/**/
     470,
 /**/
     469,