patch 9.0.1605: crash when calling method on super in child constructor

Problem:    Crash when calling method on super in child constructor. (Israel
            Chauca Fuentes)
Solution:   Clear the type list. (Ernie Rael, closes #12489, closes #12471)
diff --git a/src/userfunc.c b/src/userfunc.c
index c30c352..8facd2f 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -5651,8 +5651,8 @@
     //    type_T	**uf_arg_types;
     //    type_T	*uf_ret_type;
 
-    ufunc->uf_type_list.ga_len = 0;
-    ufunc->uf_type_list.ga_data = NULL;
+    // make uf_type_list empty
+    ga_init(&ufunc->uf_type_list);
 
     // TODO:   partial_T	*uf_partial;