MDEV-19273: Server crash in MDL_ticket::has_stronger_or_equal_type or Assertion `thd->mdl_context.is_lock_owner(MDL_key::TABLE, table->db.str, table->table_name.str, MDL_SHARED)' failed in mysql_rm_table_no_locks

Early report error in case of DROP SEQUENCE <non-sequence>

Do not use error variable for other purposes except error.