Offline flags should be undefined, not null

[ericclemmons]

This way, you can take advantage of default args for clean defaults:

const defaultFlags = {
 "testing": "Oy! I use this when testing!",
};

ldClient.all_flags(
 user,
 (err, flags = defaultFlags) => err ? reject(err) : resolve(flags)
);

Alternatively, support:

const ldClient = new LaunchDarkly.init(process.env.LAUNCHDARKLY_TOKEN, {
 offline: process.env.NODE_ENV === "test" ? { ... } : false,
});

But that would conflict with the .variation(...) default value signature, so...nah.

[dlau]

Hi Eric, thanks for your suggestion.

This feels like it would require a major npm version bump, as some users may be checking for a === null

Sounds fair to revisit this when we have a larger change that requires a bump to 4.x?