patch 9.0.0286: using freed memory when location list changed in autocmd

Problem:    Using freed memory when location list changed in autocmd.
Solution:   Return QF_ABORT and handle it. (Yegappan Lakshmanan,
            closes #10993)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 762fa8d..31d36ef 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -6363,5 +6363,22 @@
   cclose
 endfunc
 
+" Test for replacing the location list from an autocmd. This used to cause a
+" read from freed memory.
+func Test_loclist_replace_autocmd()
+  %bw!
+  call setloclist(0, [], 'f')
+  let s:bufnr = bufnr()
+  cal setloclist(0, [{'0': 0, '': ''}])
+  au BufEnter * cal setloclist(1, [{'t': ''}, {'bufnr': s:bufnr}], 'r')
+  lopen
+  try
+    exe "norm j\<CR>"
+  catch
+  endtry
+  lnext
+  %bw!
+  call setloclist(0, [], 'f')
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab