Default Charset Inconsistent behavior bug

[gxchenjingli]

in calss net.lingala.zip4j.ZipFile

this function

private Zip4jConfig buildConfig() {
    return new Zip4jConfig(charset, bufferSize, useUtf8CharsetForPasswords);
}

change to

private Zip4jConfig buildConfig() {
    return new Zip4jConfig(charset == null ? CHARSET_UTF_8 : charset , bufferSize, useUtf8CharsetForPasswords);
}

or

private Charset charset = null;

change to

private Charset charset = CHARSET_UTF_8;