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.

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1429,
 /**/
     1428,
 /**/