patch 8.0.0078

Problem:    Accessing freed memory in quickfix.
Solution:   Reset pointer when freeing 'errorformat'. (Domenique Pelle)

src/testdir/test_quickfix.vim

@@ -1648,3 +1648,13 @@ function! Test_Autocmd_Exception()
 
   set efm&vim
 endfunction
+
+function Test_caddbuffer()
+  " This used to cause a memory access in freed memory
+  let save_efm = &efm
+  set efm=%EEEE%m,%WWWW,%+CCCC%>%#,%GGGG%.#
+  cgetexpr ['WWWW', 'EEEE', 'CCCC']
+  let &efm = save_efm
+  cad
+  bwipe!
+endfunc