Description:
------------
When `mb_ereg` does not match, it does not empty the `$regs` array parameters.

Test script:
---------------
<?php

var_dump(mb_ereg('(a)\1', 'aa', $m));
var_dump($m);

var_dump(mb_ereg('(a)\1', 'ab', $m));
var_dump($m);

var_dump(mb_ereg('(foo)\1', 'foofoo', $m));
var_dump($m);

Expected result:
----------------
int(2)
array(2) {
  [0]=>
  string(2) "aa"
  [1]=>
  string(1) "a"
}

bool(false)
array(0) {}

int(6)
array(2) {
  [0]=>
  string(6) "foofoo"
  [1]=>
  string(3) "foo"
}

Actual result:
--------------
int(2)
array(2) {
  [0]=>
  string(2) "aa"
  [1]=>
  string(1) "a"
}

bool(false)
array(2) {
  [0]=>
  string(2) "aa"
  [1]=>
  string(1) "a"
}

int(6)
array(2) {
  [0]=>
  string(6) "foofoo"
  [1]=>
  string(3) "foo"
}