Description:
------------
The patch is self-explanatory, but:

php_end_ob_buffer contains:
  if (!OG(active_ob_buffer).status & PHP_OUTPUT_HANDLER_START) {
    /* our first call */
    status |= PHP_OUTPUT_HANDLER_START;
  }

But !var & flags will first evaluate !var and only after that evaluate the AND-operator.

In this case it doesn't have any affect as PHP_OUTPUT_HANDLER_START is 1.