patch 8.0.1404: invalid memory access on exit

Problem:    Invalid memory access on exit when autocommands wipe out a buffer.
            (gy741, Dominique Pelle)
Solution:   Check if the buffer is still valid. (closes #2449)
diff --git a/src/version.c b/src/version.c
index 1ce42a9..283a92c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1404,
+/**/
     1403,
 /**/
     1402,