patch 8.2.0419: various memory leaks in Vim9 script code

Problem:    Various memory leaks in Vim9 script code.
Solution:   Fix the leaks. (Ozaki Kiichi, closes #5814)
diff --git a/src/scriptfile.c b/src/scriptfile.c
index 838d5f6..55b1ddd 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1526,6 +1526,7 @@
 	vim_free(si->sn_vars);
 
 	vim_free(si->sn_name);
+	free_imports(i);
 	free_string_option(si->sn_save_cpo);
 #  ifdef FEAT_PROFILE
 	ga_clear(&si->sn_prl_ga);