fix: generate exception if codec/layer versions or channel headers are unrecognized

[joshtrichards]

Thanks (once again) for the useful library we use over at the Nextcloud project!

While looking into nextcloud/server#44573, I noted we might as well throw an informative exception if the codecVersion, layerVersion, or channel headers are unrecognized.

We're going to error out anyway when we try to use empty values for the array key. Instead of generating generic PHP errors when we go to set the bitRate and sampleRate or vbr_offset we can leave the user a bit less confused about the underlying cause.

I don't even know what MP3s might cause this, but seems reasonable to handle this situation cleanly if possible. :)

[jeremitu]

This is not sufficient, we need to consider CODEC_UNDEFINED, which is not covered by the tables:

        if ($this->codecVersion == self::CODEC_UNDEFINED) {
            throw new \Exception('Codec undefined');
        }

[kesselb]

@joshtrichards mind to update your pr with jeremitu's suggestion?

I will patch the copy in nextcloud/3rdparty then.