Add support for hitting cancel if using token id

When using a provider that uses Token ID option (like Apple) a user hitting cancel with no longer cause the app to crash.

Users who do this will now be taken back to the sign in page.

This was already working for other providers that didn't use this option but wasn't supported for providers that did use it.

src/server/lib/oauth/callback.js

@@ -38,12 +38,23 @@ export default async (req, provider, callback) => {
       code,
       provider,
       (error, accessToken, refreshToken, results) => {
-        // @TODO Handle error
         if (error || results.error) {
           logger.error('OAUTH_GET_ACCESS_TOKEN_ERROR', error, results, provider.id, code)
+          return callback(error || results.error)
         }
 
         if (provider.idToken) {
+
+          // If we don't have an ID Token most likely the user hit a cancel
+          // button when signing in (or the provider is misconfigured).
+          //
+          // Unfortunately, we can't tell which, so we can't treat it as an
+          // error, so instead we just returning nothing, which will cause the
+          // user to be redirected back to the sign in page.
+          if (!results || !results.id_token) {
+            return callback()
+          }
+
           // Support services that use OpenID ID Tokens to encode profile data
           _decodeToken(
             provider,