Does not declare variable when used in preg_match function call

php

``` php
if (! preg_match('some regex here', $subject, $regs)) {
```

zephir

```
if !(preg_match("some regex here", subject, regs)) {
```

this will crash zephir because `regs` was not declared and initialized before.

fix

```
var regs;
let regs = null;
if !(preg_match("some regex here", subject, regs)) {
```
