modules_k/pua: Fixed double-free in pua

(cherry picked from commit 5387288eac896a0710fb1c55cc4837e973e04946)

modules_k/pua/send_subscribe.c

@@ -623,6 +623,7 @@ faked_error:
 		presentity->record_route.len= record_route.len;
 		size+= record_route.len;
 		pkg_free(record_route.s);
+		record_route.s = NULL;
 	}
 
 	presentity->contact.s= (char*)presentity + size;