patch 7.4.2313
Problem:    Crash when deleting an augroup and listing an autocommand.
            (Dominique Pelle)
Solution:   Make sure deleted_augroup is valid.
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 6db3bf7..7d786c8 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -183,3 +183,12 @@
   redir END
   call assert_true(match(res, "W19:") < 0)
 endfunc
+
+func Test_augroup_deleted()
+  " This caused a crash
+  augroup x
+  augroup! x
+  au VimEnter * echo
+  au VimEnter
+endfunc
+