patch 8.0.0565: using freed memory in :caddbuf

Problem:    Using freed memory in :caddbuf after clearing quickfix list.
            (Dominique Pelle)
Solution:   Set qf_last to NULL.
diff --git a/src/version.c b/src/version.c
index 048953d..a68b999 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    565,
+/**/
     564,
 /**/
     563,