[Self-signed certificate; v5.x] E017: Network error

### Which version of floccus are you using?

5.0.10

### Sync method

Nextcloud Bookmarks

### Which browser are you using? In case you are using the phone App, specify the Android or iOS version and device please.

Brave

Version 1.63.169 Chromium: 122.0.6261.111

### Which version of Nextcloud Bookmarks are you using? (if relevant)

13.1.3

### Which version of Nextcloud? (if relevant)

28.0.3

### What kind of WebDAV server are you using? (if relevant)

_No response_

### Describe the Bug

I get a "E017: Network error: Check your network connection and your account details" after upgrading to 5.0.10. I am using a Nextcloud instance hosted on my private network. The site is accessible over 443, and is using a self-signed certificate. The certificate is not expired, but the browser marks the site as not secure because it is self-signed. I'm not sure this is totally relevant, because with the last version of Floccus 4, this did not seem to matter. All I had to do was navigate to the Nextcloud site and accept the security warning, and everything worked fine. Now I get this error. I've tried deleting the profile and recreating it, which did not help.

### Expected Behavior

I expected my bookmarks to continue to sync with Nextcloud Bookmarks as they have always done.

### To Reproduce

Click the "sync now" button or click the "sync all profiles" button.

### Debug log provided

- [ ] I have provided a debug log file

I would but it generates a 0 byte file so there's nothing to attach.