patch 9.1.0728: [security]: heap-use-after-free in garbage collection with location list user data

Problem:  heap-use-after-free in garbage collection with location list
          user data.
Solution: Mark user data as in use when no other window is referencing
          the location list (zeertzjq)

fixes: neovim/neovim#30371
closes: #15683

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/quickfix.c

@@ -8011,6 +8011,10 @@ set_ref_in_quickfix(int copyID)
 	    abort = mark_quickfix_ctx(win->w_llist_ref, copyID);
 	    if (abort)
 		return abort;
+
+	    abort = mark_quickfix_user_data(win->w_llist_ref, copyID);
+	    if (abort)
+		return abort;
 	}
     }