Use retrun value of zephir_parse_file() trigger a signal 11: SIGSEGV

[heyuuu]

Describe the bug
The process interrupted by signal 11: SIGSEGV when do same logic in return val of zephir_parse_file twice.

To Reproduce
Run this code:

function once()
{
    $code = "class Translate {}";
    $ast  = zephir_parse_file($code, '/test_filename.zep');

    try {
        $node = $ast[0];

        unset($node['type']);
        unset($node['file']);
        unset($node['line']);
        unset($node['char']);

        throw new \Exception();
    } catch (\Exception $e) {
    }
}

once();
once(); // It trigger error in second times

Expected behavior
Don't trgger error.

Environment (please complete the following information):

• OS: MacOS 10.14
• Zephir Parser version: development(b8e3162)
• Installation type: compiling from source
• Compiler version [e.g. gcc 5.4.0]: Apple LLVM version 10.0.0 (clang-1000.11.45.5)
• PHP version [e.g. 7.2.4 ( NTS )]: 7.0.30