patch 8.1.0450: build failure without the +fold feature

Problem:    Build failure without the +fold feature.
Solution:   Add #ifdef.
diff --git a/src/version.c b/src/version.c
index a0aa0dc..88b3a53 100644
--- a/src/version.c
+++ b/src/version.c
@@ -793,6 +793,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    450,
+/**/
     449,
 /**/
     448,