vim-patch:8.0.0590: cannot add a context to locations

Problem:    Cannot add a context to locations.
Solution:   Add the "context" entry in location entries. (Yegappan Lakshmanan,
            closes vim/vim#1012)

8f77c5a4ec

src/nvim/eval.c

@@ -5173,6 +5173,8 @@ bool garbage_collect(bool testing)
     ABORTING(set_ref_list)(sub.additional_elements, copyID);
   }
 
+  ABORTING(set_ref_in_quickfix)(copyID);
+
   bool did_free = false;
   if (!abort) {
     // 2. Free lists and dictionaries that are not referenced.