Confusing error when type is undefined in ZipObject.async

[Darker]

I forgot to add type parameter to ZipObject.async:

    settings = JSON.parse(await zip.file(SETTINGS_DEFAULT_PATH).async());

The error:

 TypeError: Cannot read property 'toLowerCase' of undefined
    at ZipObject.internalStream (D:\techsys\webapp\WebDozor\jszip.js:4096:30)
    at ZipObject.async (D:\techsys\webapp\WebDozor\jszip.js:4122:21)
    at __dirname (D:\techsys\webapp\WebDozor\make_package.js:46:73)

The line:

    internalStream: function (type) {
        var outputType = type.toLowerCase();
        var askUnicodeString = outputType === "string" || outputType === "text";
        if (outputType === "binarystring" || outputType === "text") {
            outputType = "string";
        }

Some input check would solve this issue. Such as if(typeof type!="string") throw new Error("Type must be string value.");

[dduponchel]

The method generateAsync() has this check (almost, the type isn't checked). I'll copy this check to async().