[Bug]: Nextcloud crashes when attempting to add an account with a client certificate

[akechi-haruka]

⚠️ Before submitting, please verify the following: ⚠️

• [x] This is a bug, not a question or a configuration issue.
• [x] This issue is not already reported on Github (I've searched it).
• [x] Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• [x] I agree to follow Nextcloud's Code of Conduct

Bug description

When I attempt to add an account to a nextcloud installation that is behind a reverse proxy requiring a client certificate, nextcloud crashes after adding the account and then will not save the certificate causing the account to be permantently offline.

Steps to reproduce

1. Install nextcloud
2. Enter server address
3. Click the option to provide a client certificate when connection fails
4. Provide the file (with no password)
5. Nextcloud will successfully connect and start authentication through the browser
6. Finish with the authentication process
7. Select a local folder to sync to
8. Main window will open for a second and then crash
9. Upon restarting, the account is offline with "sslv3 alert: certificate required"

Expected behavior

The client certificate is saved and nextcloud does not crash.

Which files are affected by this bug

N/A

Operating system

Windows

Which version of the operating system you are running.

Windows 10

Package

Official Windows MSI

Nextcloud Server version

30.0.0

Nextcloud Desktop Client version

3.14.3

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• [x] Default internal user-backend
• [ ] LDAP/ Active Directory
• [ ] SSO - SAML
• [ ] Other

Nextcloud Server logs

No response

Additional info

Crash log:

Faulting application name: nextcloud.exe, version: 3.14.3.55943, time stamp: 0x67238c6c
Faulting module name: Qt6Core.dll, version: 6.7.2.0, time stamp: 0x66bfce9d
Exception code: 0xc0000005
Fault offset: 0x00000000000dfee6
Faulting process ID: 0x14e4
Faulting application start time: 0x01db308083f7ab2c
Faulting application path: C:\Program Files\Nextcloud\nextcloud.exe
Faulting module path: C:\Program Files\Nextcloud\Qt6Core.dll
Report ID: 830499a0-ae47-40f9-8f47-7595ffa87cc3
Faulting package full name: 
Faulting package-relative application ID: 

Client log:

nextcloud.log