patch 8.2.1561: using NULL pointers in fold code

Problem:    Using NULL pointers in fold code.
Solution:   Avoid using a NULL pointer. (Dominique Pellé, closes #6831,
            closes #6831)
diff --git a/src/version.c b/src/version.c
index 29f4363..80c3998 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1561,
+/**/
     1560,
 /**/
     1559,