The crash happens when 'skip-grant-tables' is enabled.
We skip the filling of I_S privilege tables 
if acl_cache is not initialized.


mysql-test/r/skip_grants.result:
  test result
mysql-test/t/skip_grants.test:
  test case
sql/sql_acl.cc:
  skip filling of I_S privilege tables
  if acl_cache is not initialized