patch 9.0.1429: invalid memory access when ending insert mode

Problem:    Invalid memory access when ending insert mode.
Solution:   Check if the insert_skip value is valid.
diff --git a/src/version.c b/src/version.c
index f25f59f..23e69b3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1429,
+/**/
     1428,
 /**/
     1427,