MDEV-28266 Crash in Field_string::type_handler when calling procedures

on_table_fill_finished() should always be done at the end of open() even if result is not Select_materialize but (for example) Select_fetch_into_spvars.

Author: sanja-byelkin

sql/sql_cursor.cc

@@ -80,19 +80,7 @@ class Select_materialize: public select_unit
  Select_materialize(THD *thd_arg, select_result *result_arg):
  select_unit(thd_arg), result(result_arg), materialized_cursor(0) {}
  virtual bool send_result_set_metadata(List<Item> &list, uint flags);
- bool send_eof()
- {
- if (materialized_cursor)
- materialized_cursor->on_table_fill_finished();
- return false;
- }
-
- void abort_result_set()
- {
- if (materialized_cursor)
- materialized_cursor->on_table_fill_finished();
- }
-
+ bool send_eof() { return false; }
  bool view_structure_only() const
  {
  return result->view_structure_only();
@@ -334,6 +322,8 @@ int Materialized_cursor::open(JOIN *join __attribute__((unused)))
  result->abort_result_set();
  }
 
+ on_table_fill_finished();
+
  return rc;
 }