Describe the bug
On the SSL Certificates tab, adding a custom certificate does not open a drop-down dialog, hence custom certificates cannot be added.
Adding a Let's Encrypt certificate via the same button works fine.

Nginx Proxy Manager Version
v2.9.13

To Reproduce
Steps to reproduce the behavior:

1. Go to the "SSL Certificates" tab
2. Click on "Add SSL Certificate"
3. Click on "Custom"
4. No action occurs.

Expected behavior
A drop down dialog is presented to allow the user to add a certificate

Screenshots
N/A - No error or screen of any kind is presented. But something should happen when you click this button.

Operating System
Unraid 6.9.2 (via Docker)

Additional context