Errors in session-data-defaults.js get swallowed and do not crash the kit

[edwardhorsford]

If there is a syntax error or bug in session-data-defaults.js it seems like these errors get swallowed.

If I introduce an error, the kit keeps running - if you restart the kit, it seems the data isn't loaded at all - but as a user it's hard to tell this has happened - you'd have to have a good idea what was wrong.

Even if you know there's an issue with the file, without the raw error it's hard to work out what the error was.

Chatting with @nataliecarey it seems this section of the code is responsible:

govuk-prototype-kit/lib/session.js

Lines 87 to 95 in c0e7079

	let sessionDataDefaults
	const sessionDataDefaultsFile = path.join(projectDir, 'app', 'data', 'session-data-defaults.js')
	try {
	sessionDataDefaults = require(sessionDataDefaultsFile)
	} catch (e) {
	sessionDataDefaults = {}
	}

What I'd expect

Ideally the kit would crash and show an error.

[nataliecarey]

I've raised a PR with the fix for this: #2417