patch 8.0.0322: possible overflow with corrupted spell file

Problem:    Possible overflow with spell file where the tree length is
            corrupted.
Solution:   Check for an invalid length (suggested by shqking)
diff --git a/src/version.c b/src/version.c
index 7a3d215..c1a5186 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    322,
+/**/
     321,
 /**/
     320,