It did that, but now that you've got a certificate with both hostnames, there's no certificate issue any longer. Also, your HTTP site redirected all non-encrypted traffic to the www subdomain with HTTPS, so normally users wouldn't be bothered by a warning, as normally users would not end up to the HTTPS non-www hostname.
I tested the above with the command:
openssl s_client -connect slidepipe.com:443 -servername slidepipe.com | openssl x509 -noout -text
Which shows the contents of the certificate provided by the webserver for the hostname earlier in the command.