patch 8.0.1280: Python None cannot be converted to a Vim type

Problem:    Python None cannot be converted to a Vim type.
Solution:   Convert it to v:none. (Ken Takata)
diff --git a/src/version.c b/src/version.c
index df0e501..85f5296 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1280,
+/**/
     1279,
 /**/
     1278,