patch 8.2.0467: Vim9: some errors are not tested

Problem:    Vim9: some errors are not tested
Solution:   Add more tests.  Fix that Vim9 script flag is not reset.
diff --git a/src/scriptfile.c b/src/scriptfile.c
index 55b1ddd..a7af4e9 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1274,6 +1274,7 @@
 
 	// loading the same script again
 	si->sn_had_command = FALSE;
+	si->sn_version = 1;
 	current_sctx.sc_sid = sid;
 
 	ht = &SCRIPT_VARS(sid);