patch 8.2.4293: Vim9: when copying a list it gets type list<any>

Problem:    Vim9: when copying a list it gets type list<any> even when the
            original list did not have a type.
Solution:   Only set the type when the original list has a type. (closes #9692)
diff --git a/src/list.c b/src/list.c
index 86c1679..3a6ea97 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1216,7 +1216,11 @@
     copy = list_alloc();
     if (copy != NULL)
     {
-	copy->lv_type = alloc_type(top || deep ? &t_list_any: orig->lv_type);
+	if (orig->lv_type == NULL)
+	    copy->lv_type = NULL;
+	else
+	    copy->lv_type = alloc_type(top || deep
+						 ? &t_list_any: orig->lv_type);
 	if (copyID != 0)
 	{
 	    // Do this before adding the items, because one of the items may