dbAuth: Catch fetch failure in getToken

[Tobbe]

We have this comment in useToken()

redwood/packages/auth/src/AuthProvider/useToken.ts

Lines 7 to 14 in 4b734d3

	/**
	* Clients should always return null or token string.
	* It is expected that they catch any errors internally.
	* This catch is a last resort effort in case any errors are
	* missed or slip through.
	*/
	try {
	const token = await authImplementation.getToken()

And for example our Netlify auth implementation does this:

redwood/packages/auth-providers/netlify/web/src/netlify.ts

Lines 68 to 78 in 4b734d3

	getToken: async () => {
	try {
	// The client refresh function only actually refreshes token
	// when it's been expired. Don't panic
	await netlifyIdentity.refresh()
	const user = await netlifyIdentity.currentUser()
	return user?.token?.access_token || null
	} catch {
	return null
	}
	},

But dbAuth let the exception slip through to useToken.
This PR adds a catch to the promise and returns null, just like Netlify (and others)

Before merging this though, I need to make sure I'm not undoing the fix @standup75 did in #8284
(@standup75 can you say off the top of your head if my code will work or not?)

[standuprey]

finally will still get called, so lgtm, thanks for asking!