patch 8.2.4632: using freed memory in flatten()

Problem:    Using freed memory in flatten().
Solution:   Clear typval after recursing into list.
diff --git a/src/version.c b/src/version.c
index 9d78a0e..962fa0b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4632,
+/**/
     4631,
 /**/
     4630,