fixup use_after_free in the pat_ref_delete_by_id

[peter cai]

I found there is use_after_free bug in the pat_ref_delete_by_id.

diff --git a/haproxy/src/pattern.c b/haproxy/src/pattern.c
index 4bd6924..0bd35a7 100644
--- a/haproxy/src/pattern.c
+++ b/haproxy/src/pattern.c
@@ -1573,14 +1573,14 @@ int pat_ref_delete_by_id(struct pat_ref *ref,
struct pat_ref_elt *refelt)
        /* delete pattern from reference */
        list_for_each_entry_safe(elt, safe, &ref->head, list) {
                if (elt == refelt) {
+                       list_for_each_entry(expr, &ref->pat, list)
+                               pattern_delete(expr, elt);
+
                        list_del(&elt->list);
                        haproxy_free(elt->sample);
                        haproxy_free(elt->pattern);
                        haproxy_free(elt);

-                       list_for_each_entry(expr, &ref->pat, list)
-                               pattern_delete(expr, elt);
-
                        return 1;
                }
        }