[Bug]: Empty web link value in theming configuration not accepted

[brainchild0]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Theming settings feature a field Web link, which is by default populated with the address for the developer's web site, operated by Nextcloud GmbH.

However, the address may be removed from configuration only by replacing with another. An empty value is not accepted.

Steps to reproduce

Attempt to submit empty value for Web link.

Empty value is rejected.

Expected behavior

Empty value is accepted.

Installation method

Community Web installer on a VPS or web space

Nextcloud Server version

25

Operating system

Other

PHP engine version

PHP 7.4

Web server

Apache (supported)

Database engine version

MariaDB

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

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

Encryption is Enabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            ***********,
            ***********
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "25.0.9.2",
        "overwrite.cli.url": "",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance": false,
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpauth": 1,
        "theme": "",
        "loglevel": 0,
        "mysql.utf8mb4": true,
        "updater.release.channel": "stable",
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "app_install_overwrite": [
            "social",
            "checksum",
            "contacts",
            "apporder",
            "external",
            "files_markdown",
            "passman",
            "quota_warning",
            "issuetemplate",
            "files_readmemd",
            "bookmarks",
            "ocsms"
        ],
        "encryption.legacy_format_support": false,
        "encryption.key_storage_migrated": false,
        "simpleSignUpLink.shown": false,
        "memcache.local": "\\OC\\Memcache\\APCu",
        "default_phone_region": "US"
    }
}

List of activated Apps

Enabled:
  - activity: 2.17.0
  - admin_audit: 1.15.0
  - bookmarks: 12.1.0
  - calendar: 4.4.3
  - checksum: 1.2.2
  - circles: 25.0.0
  - cloud_federation_api: 1.8.0
  - comments: 1.15.0
  - contacts: 5.3.2
  - contactsinteraction: 1.6.0
  - dashboard: 7.5.0
  - dav: 1.24.0
  - encryption: 2.13.0
  - external: 5.0.2
  - federatedfilesharing: 1.15.0
  - federation: 1.15.0
  - files: 1.20.1
  - files_external: 1.17.0
  - files_markdown: 2.4.1
  - files_pdfviewer: 2.6.0
  - files_rightclick: 1.4.0
  - files_sharing: 1.17.0
  - files_trashbin: 1.15.0
  - files_versions: 1.18.0
  - firstrunwizard: 2.14.0
  - guests: 2.5.0
  - issuetemplate: 0.7.0
  - logreader: 2.10.0
  - lookup_server_connector: 1.13.0
  - mail: 2.2.7
  - nextcloud_announcements: 1.14.0
  - notes: 4.8.1
  - notifications: 2.13.1
  - oauth2: 1.13.1
  - passman: 2.4.5
  - password_policy: 1.15.0
  - photos: 2.0.1
  - privacy: 1.9.0
  - provisioning_api: 1.15.0
  - quota_warning: 1.17.0
  - recommendations: 1.4.0
  - related_resources: 1.0.4
  - serverinfo: 1.15.0
  - settings: 1.7.0
  - sharebymail: 1.15.0
  - side_menu: 3.10.3
  - support: 1.8.0
  - survey_client: 1.13.0
  - systemtags: 1.15.0
  - tasks: 0.15.0
  - text: 3.6.0
  - theming: 2.0.1
  - theming_customcss: 1.14.0
  - twofactor_backupcodes: 1.14.0
  - updatenotification: 1.15.0
  - user_ldap: 1.15.0
  - user_status: 1.5.0
  - viewer: 1.9.0
  - weather_status: 1.5.0
  - workflowengine: 2.7.0
Disabled:
  - bruteforcesettings
  - suspicious_login
  - twofactor_totp

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"a4Z62IL9OzFY0y4yF66F","level":2,"time":"2023-07-25T02:50:03+00:00","remoteAddr":"","user":"--","app":"OC\\Log\\Rotate","method":"","url":"--","message":"Log file \"/var/www/vhosts/<domainname>/private/nextclouddata/nextcloud.log\" was over 104857600 bytes, moved to \"/var/www/vhosts/<domainname>/private/nextclouddata/nextcloud.log.1\"","userAgent":"--","version":"25.0.9.2","data":{"app":"OC\\Log\\Rotate"},"id":"64bf6b83cd618"}

Additional info

No response