captcha - keep consistency with token send to validation (#12195)

[Sentry
error](https://twenty-v7.sentry.io/issues/6494360796/events/322590f8af5c4475beebb66e5f22a2f7/?environment=prod&project=4507072499810304&query=is%3Aunresolved%20issue.priority%3A%5Bhigh%2C%20medium%5D&referrer=previous-event&seerDrawer=true&sort=date&stream_index=6)
raised because of invalid argument type (undefined in some case when
string is expected)

closes https://github.com/twentyhq/core-team-issues/issues/869 and
closes https://github.com/twentyhq/twenty/issues/12208

packages/twenty-server/src/engine/core-modules/captcha/captcha.guard.ts

@@ -29,7 +29,7 @@ export class CaptchaGuard implements CanActivate {
     } else {
       await this.metricsService.incrementCounter({
         key: MetricsKeys.InvalidCaptcha,
-        eventId: token,
+        eventId: token || '',
       });
 
       throw new BadRequestException(