message: fix swoole_table  iterator coredump
diff: @@ -788,10 +788,17 @@ static PHP_METHOD(swoole_table, current)
  RETURN_FALSE;
  }
  swTableRow *row = swTable_iterator_current(table);
  + if (row)
  + {
  swTableRow_lock(row);
  php_swoole_table_row2array(table, row, return_value);
  swTableRow_unlock(row);
  }
  + else
  + {
  + RETURN_NULL();
  + }
  +}
  static PHP_METHOD(swoole_table, key)
  {
  @@ -802,10 +809,17 @@ static PHP_METHOD(swoole_table, key)
  RETURN_FALSE;
  }
  swTableRow *row = swTable_iterator_current(table);
  + if (row)
  + {
  swTableRow_lock(row);
  RETVAL_STRING(row->key);
  swTableRow_unlock(row);
  }
  + else
  + {
  + RETURN_NULL();
  + }
  +}
  static PHP_METHOD(swoole_table, next)
  {
  