patch 8.2.0642: Vim9: using invalid index

Problem:    Vim9: using invalid index.
Solution:   Check index for being valid.  Fix memory leak.
diff --git a/src/version.c b/src/version.c
index 3829af5..590c392 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    642,
+/**/
     641,
 /**/
     640,