patch 8.0.0352: not easy to see when a typval needs to be cleared

Problem:    The condition for when a typval needs to be cleared is too
            complicated.
Solution:   Init the type to VAR_UNKNOWN and clear it always.

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    352,
 /**/
     351,
 /**/