fix(TemplateLayout): Refactor user ID handling

[solracsf]

Resolves: #54166

Stack trace

{
  "reqId": "82V7qlVkqgH0JmCmzvEl",
  "level": 3,
  "time": "2026-02-03T18:18:05+01:00",
  "remoteAddr": "185.204.254.31",
  "user": "--",
  "app": "index",
  "method": "GET",
  "url": "/apps/files/?dir=/&fileid=60365521",
  "scriptName": "/index.php",
  "message": "userId cannot be an empty string",
  "userAgent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36",
  "version": "31.0.13.1",
  "exception": {
    "Exception": "InvalidArgumentException",
    "Message": "userId cannot be an empty string",
    "Code": 0,
    "Trace": [
      {
        "file": "/var/www/nextcloud/lib/private/Config/UserConfig.php",
        "line": 152,
        "function": "assertParams",
        "class": "OC\\Config\\UserConfig",
        "type": "->",
        "args": [
          "",
          "avatar",
          "version"
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/private/AllConfig.php",
        "line": 282,
        "function": "hasKey",
        "class": "OC\\Config\\UserConfig",
        "type": "->",
        "args": [
          "",
          "avatar",
          "version"
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/private/TemplateLayout.php",
        "line": 135,
        "function": "getUserValue",
        "class": "OC\\AllConfig",
        "type": "->",
        "args": [
          false,
          "avatar",
          "version",
          0
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/private/legacy/OC_Template.php",
        "line": 120,
        "function": "__construct",
        "class": "OC\\TemplateLayout",
        "type": "->",
        "args": [
          "user",
          "files"
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/public/AppFramework/Http/TemplateResponse.php",
        "line": 189,
        "function": "fetchPage",
        "class": "OC_Template",
        "type": "->",
        "args": [
          []
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php",
        "line": 159,
        "function": "render",
        "class": "OCP\\AppFramework\\Http\\TemplateResponse",
        "type": "->",
        "args": []
      },
      {
        "file": "/var/www/nextcloud/lib/private/AppFramework/App.php",
        "line": 161,
        "function": "dispatch",
        "class": "OC\\AppFramework\\Http\\Dispatcher",
        "type": "->",
        "args": [
          {
            "__class__": "OCA\\Files\\Controller\\ViewController"
          },
          "index"
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/private/Route/Router.php",
        "line": 315,
        "function": "main",
        "class": "OC\\AppFramework\\App",
        "type": "::",
        "args": [
          "OCA\\Files\\Controller\\ViewController",
          "index",
          {
            "__class__": "OC\\AppFramework\\DependencyInjection\\DIContainer"
          },
          {
            "_route": "files.view.index"
          }
        ]
      },
      {
        "file": "/var/www/nextcloud/lib/base.php",
        "line": 1063,
        "function": "match",
        "class": "OC\\Route\\Router",
        "type": "->",
        "args": [
          "/apps/files/"
        ]
      },
      {
        "file": "/var/www/nextcloud/index.php",
        "line": 24,
        "function": "handleRequest",
        "class": "OC",
        "type": "::",
        "args": []
      }
    ],
    "File": "/var/www/nextcloud/lib/private/Config/UserConfig.php",
    "Line": 1668,
    "message": "userId cannot be an empty string",
    "exception": [],
    "CustomMessage": "userId cannot be an empty string"
  },
  "id": "6982e36d39264"
}

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[susnux]

How can userId ever be an empty string? Either its null or the userId which has to be not empty.
If there is a case where its an empty string here, then its triggered far up in the logic.

[solracsf]

I fully understand your point; the fact is the the only reports (and my own logs) about "UID empty string" are these.

If there were problems at the IUserSession::class level, there would be way more, and different, reports, no?

[susnux]

Can you reproduce the issue? I was not able to do so.
If you can, then you could add some debugging to the User class when the user id is set to the empty string, would be good to get the stack trace there.