patch 8.0.0155: ubsan complains about NULL pointer

Problem:    When sorting zero elements a NULL pointer is passed to qsort(),
            which ubsan warns for.
Solution:   Don't call qsort() if there are no elements. (Dominique Pelle)
diff --git a/src/version.c b/src/version.c
index 368e6be..d88c03b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    155,
+/**/
     154,
 /**/
     153,