Web-Interface also creates entry for SSL-Cert that failed to initially create using Letsencrypt

[typoworx-de]

Checklist

• Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
  Yes
• Are you sure you're not using someone else's docker image?
  Yes
• If having problems with Lets Encrypt, have you made absolutely sure your site is accessible from outside of your network?
  Yes

Describe the bug
Tried to roll-out some SSL>Letsencrypt certs and got "Internal error" trying to deploy them using Letsencrypt and Cloudflare API (see #628).

Anyway there will be created an Cert-Entry in SSL Certificates list for an invalid cert. This is very confusing and does not make sense!

• What version of Nginx Proxy Manager is reported on the login page?
  v2.5.0

To Reproduce
Steps to reproduce the behavior:
see #628

Expected behavior
Either successfully fetch a cert and create the entry or throw an error and don't create a cert-entry in the SSL Certificates list!

Screenshots
If applicable, add screenshots to help explain your problem.

Operating System
Docker + Ubuntu 20

Additional context